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1 Page 1 of 29 Section 04-05: Suspension, Computer Controlled 1997 Town Car Workshop Manual DIAGNOSIS AND TESTING Procedure revision date: 05/16/2000 Suspension, Computer Controlled Inspection and Verification 1. Verify the customer's concern by operating the vehicle to duplicate the condition. 2. Inspect to determine if one of the following mechanical or electrical concerns apply: VISUAL INSPECTION CHART Mechanical Shock absorber failure Leak from air line(s) Leak from air spring(s) Ruptured air spring(s) Height sensor damaged Height sensor off ball studs Electrical Open Fuses: Power Distribution Box Fuse U (30A), Fuse Junction Panel, Fuse 7 (15A) Loose Connectors Corroded Connectors Air Suspension Service Switch OFF 3. If inspection reveals obvious concerns that can be readily identified, service as required. 4. If the concern(s) remains after the inspection, determine the symptom(s) and go to the Symptom Chart. Using the Super Star II This control module is diagnosed using Rotunda Super Star II Tester B or equivalent. The test connector used to communicate with the EVO control module is located on the RH side of the luggage compartment. When the tester is connected, the engine is started and the HOLD/TEST button is latched down, the EVO controller will respond by sending a code 10 to the Super Star Tester which represents "Diagnostics mode entered." If diagnostic trouble code (DTC) 10 is not displayed, go to Pinpoint Test R. DTC Index Air Suspension Diagnostic Trouble Codes And Pinpoint Test Index DTC Pinpoint Test Description Service Priority 10 Diagnostics Entered, Auto Test in Progress 11 Vehicle Passes a 12 Auto Tested Passed, Perform Manual Inputs 13 Auto Test Failed, Perform Manual Inputs 15 Drive Cycle Errors Detected 16 EVO Diagnostic Trouble Code (Refer to Section 11-00) 17 EVO Diagnostic Trouble Code (Refer to Section 11-00) 18 EVO Diagnostic Trouble Code (Refer to Section 11-00) 23 b Functional Test, Vent Rear 26 b Functional Test, Compress Rear 28 H Steering Select Switch t Detected 4th 31 b Functional Test, Air Compressor Relay Toggle 32 b Functional Test, Vent Solenoid Toggle 33 b Functional Test, Air Spring Solenoid Toggle 35 Drive Cycle Error Codes Erased OK 39 C Compressor Relay Control Circuit Short to B+ 2nd 40 C Compressor Relay Control Circuit Short to Ground 2nd 42 D Air Spring Solenoid Valve Short to Ground 2nd 43 E Air Spring Solenoid Valve Short to Battery 2nd 44 F Vent Solenoid Valve Short to Battery 2nd 45 G Short in Vent Solenoid Valve Circuit 2nd 46 M Air Suspension Height Sensor Supply Circuit Shorted 2nd 51 J Unable to Detect Lowering of Rear 3rd 54 K Unable to Detect Raising of Rear 3rd 55 P Speed Greater than 15 MPH t Detected 4th 60 Q Service Switch Shorted to Battery 2nd 61 R Service Switch Shorted to Ground or Open 2nd 68 L Short in Rear Air Suspension Height Sensor Circuit 2nd 70 Replace Control Module 71 N Air Suspension Height Sensor Circuit Open 3rd 72 B Did t Detect Four Open and Closed Door Signals 4th 74 EVO Diagnostic Trouble Code (Refer to Section 11-00)

2 Page 2 of A Control Module Detects Low Battery Voltage 1st S Unable to Enter Auto Test Diagnostics or Warning Light Remains On After Vehicle Passes (Code 11) a If vehicle is still low or high in rear, check ride height. Refer to Adjustments. b Functional Tests after Auto Test. Diagnostic Instructions This part of diagnostics is divided into three areas: Drive Cycle Diagnostics Auto Test Diagnostics Functional Tests Drive Cycle Diagnostics To assist the technician in correcting intermittent air suspension errors, air suspension systems have the ability to store DTCs. When the warning light has been activated, the control module will store that DTC for 80 ignition cycles. If there is no repeat of the same error during these 80 ignition cycles, the control module will erase the DTC. The technician can retrieve the stored DTC by performing DRIVE CYCLE DIAGNOSTICS. Drive Cycle Diagnostics Test Procedure AUTO TEST DIAGNOSTICS At the beginning of the automatic portion of the test, the control module (5A919) checks for damaged control module (DTC 70), for unstable battery voltage (DTC 80), then for shorted or open conditions that would create DTCs 39 through 46, and 68 through 71. If shorts or opens are detected, the automatic portion of the test is ended and a DTC 13 (Auto Test Failed) will be displayed on the Super Star II tester. If no shorts or opens are detected, the automatic portion of the test continues. The control module attempts to raise and lower the vehicle to verify that all three air suspension height sensor states (trim, high, and low) can be reached. A properly functioning vehicle will be at trim height at the end of the Auto Test. If all three states are not reached, the Auto Test will end and again a DTC 13 will be displayed. A DTC 12 will be displayed at the end of the Auto Test only if everything checked to this point is functional. After DTC 12 (or DTC 13) is displayed, the control module is ready to check for manual inputs. The manual inputs check the steering sensor and the door courtesy lamp switch circuits. During the manual test, the control module continually monitors the door Circuit 344 (BK/Y) and the steering sensor Circuits 633 (R) and 634 (BR) for activity. To pass the manual test the control module must detect that all four doors have been opened and closed, and that the steering wheel has been turned at least one quarter turn in each direction. The EVO steering select switch must be cycled through all three positions. After the manual test, the Star tester button must be toggled or the control module will continue to monitor the manual test inputs indefinitely. Either a DTC 11 (Air Suspension OK) or other DTCs will be displayed at this time. After the Auto/Manual tests, the DTCs will be displayed automatically. Each DTC detected will be displayed for about 15 seconds. The code display will continue until all DTCs have been displayed. The display will repeat the DTC until the Star test button is released (up). Write down all DTCs, then release pressed tester button. DO NOT disconnect or turn OFF the tester. The tester is ready to enter the Functional Test if a DTC 11 has been displayed.

3 Page 3 of 29 AA1 CHECK FOR DTCs NOTE: Rotunda Super Star II Tester B or equivalent must be used for this procedure. Super Star Tester may not be used. Remove all extra loads from luggage and passenger compartments. Set Super Star II: EEC/MCU Setting, FAST codes Turn ignition switch OFF. Turn air suspension switch (RH side of luggage compartment) OFF, then ON. Remove RH luggage compartment trim panel. Refer to Section NOTE: Make sure STAR test button is in HOLD (up) position before connecting to vehicle. Connect Star Tester to air suspension test connector C459. If battery is weak, connect battery charger to maintain battery level and turn ignition switch to RUN. Wait at least two seconds, then press Star Tester button so it remains in the TEST (down) position. Within 20 seconds, a DTC 10 should be displayed. Is there any code displayed? GO toaa2. CHECK tester connections. RETEST system. AA2 CHECK FOR DTC 10 Check the tester display for DTC. Is DTC 10 displayed? System is in AUTO Test Mode. GO to AA4. GO to AA3. AA3 CHECK FOR DTC 80 Check the tester display for DTC. Is DTC 80 displayed? GO to Pinpoint Test Step M1. GO to AA1. AA4 CHECK FOR DTC 11 DTC 10 will be displayed for up to two minutes. DO NOT put any weight on vehicle while DTC 10 is displayed. When Auto Test is complete a DTC 12 (Auto Test passed) or DTC 13 (Auto Test failed) will be displayed. NOTE: The following manual inputs can be done in any sequence. With DTC 12 or 13 displayed: Open and close all four doors. Turn steering wheel 1/4 turn in both directions. Cycle steering select switch through three positions. Release STAR TEST button to HOLD (up) position. Wait two seconds and press button to TEST (down) position. NOTE: The DTCs will be displayed for about 15 seconds each. After all DTCs have been displayed, the DTCs will be repeated. The DTCs will continue to repeat as long as the Star tester button is in the TEST (down) position. Within 20 seconds DTCs will be displayed. Is DTC 11 displayed? Vehicle passes. EXIT Auto Test by disconnecting Star tester and turning ignition switch OFF. RECORD DTCs. REFER to Air Suspension DTC and Pinpoint Test Index for Pinpoint Tests for DTCs displayed. DO NOT disconnect or turn off Star Tester, ignition switch or air suspension switch. FUNCTIONAL TESTS CAUTION: Functional test is run only if diagnosis does not identify concern. Excessive use of the functional test could overheat the compressor or damage system electronics. Functional tests are run at the end of the Auto/Manual test procedure, and are used as an aid to diagnose the system. The only way to enter the Functional Test is by first running the Auto/Manual test. During the Functional Test the control module will attempt to cycle the components as follows: DTC 23: Vent Rear - During this test the control module will attempt to open the vent solenoid valve and air spring solenoid valves (5311) as long as the Star tester button is pressed. The rear of the vehicle will lower.

4 Page 4 of 29 NOTE: DTC 26 is normally used to inflate the air spring after installation. DTC 26: Compress Rear - During this test the control module will attempt to energize the compressor and open the spring solenoid valves as long as the Star tester button is pressed. The rear of the vehicle will rise. NOTE: The extended use of this test can cause the self-resetting circuit breaker in the compressor to open. If this happens, allow the compressor to cool down for 15 minutes. Then, restart the diagnostic procedures. DTC 31: Air Compressor Relay Toggle - During this test, the control module will attempt to cycle the compressor relay ON for one second and OFF for one second repeatedly. This cycle will repeat for as long as the Star tester button is pressed. The compressor will be heard cycling ON and OFF if this test is successful. DTC 32: Vent Solenoid Valve Toggle - During this test, the vent solenoid valve is opened for one second, then closed for one second. This cycle will repeat for as long as the Star tester button is pressed. The vent solenoid valve in the air compressor will be heard cycling ON and OFF if this test is successful. DTC 33: Air Spring Solenoid Valve Toggle - During this test, both air spring solenoid valves will be opened for one second, then closed for one second repeatedly. This cycle will repeat for as long as the Star tester button is pressed. The control module cannot turn one spring solenoid valve on without turning the other solenoid valve on (Circuits 114 (BR/PK) and 115 (T/W) are tied together inside the control module). To verify that both solenoid valves operate, raise the vehicle on a hoist. Do not turn the air suspension switch OFF. Remain in Functional Test DTC 33. Then, touch each solenoid valve to verify that it is cycling ON and OFF. AB1 CHECK FOR DTCs Functional Tests are used in some of the DTC Pinpoint Tests to aid in system diagnosis. The Functional Test mode can only be entered after Auto Test has been performed. A DTC 11 or any other DTCs must be displayed before the Functional Test mode can be entered. Are DTCs displayed? GO to AB2. REPEAT Auto Test. If Auto Test cannot be entered, GO to Pinpoint Test S. AB2 CHECK FOR FUNCTIONAL TEST DTCs Release Star Tester button to the HOLD (up) position. Wait at least 20 seconds. Press Star Tester button to the TEST (down) position. DTC 23 should be displayed, then DTCs 26, 31, 32 and 33 will be displayed in order. Each DTC will be displayed for about 15 seconds. After all the DTCs are displayed, they will be repeated as long as the Star Test button is in TEST (down) position. Are functional test DTCs displayed? GO to AB3. RELEASE Star Tester button to HOLD (up) position. Wait 20 seconds and press button to TEST (down) position. If Functional Test DTCs are still not displayed, REPEAT Auto Test. AB3 PERFORM FUNCTIONAL TESTS The following chart lists the Functional Test DTCs: DTC 23 Vent Rear 26 Compress Rear Within four seconds after the desired Functional Test DTC is displayed, release the Star Tester button to the HOLD (up) position. NOTE: Waiting longer than four seconds will cause the next Function Test to be entered. As long as the Star Tester button is in the HOLD (up) position, the Functional Test will continue. NOTE: The Star Tester may or may not display the DTC for the Functional Test selected. Example: Functional Test DTC 32 is selected. Star Tester may display DTC 31, even though Functional Test 32 is being run. To exit a Functional Test, depress the Star Tester button to the TEST (down) position. The Functional Test DTCs will be displayed. The DTCs will be displayed for about 15 seconds each and will cycle. The Functional Tests may be entered and exited as often as desired. Are all Functional Tests successful? Description 31 Toggle Compressor on and off repeatedly 32 Toggle vent solenoid valve on and off repeatedly 33 Toggle air spring solenoid valves on and off repeatedly If directed here from Pinpoint Test, RETURN to original test. REFER to Air Suspension Diagnostic Trouble Codes and Pinpoint Test Index. Symptom Chart Computer Controlled Suspension Refer to the Electrical and Vacuum Troubleshooting Manual for the connector numbers cited in the pinpoint tests. Use Rotunda 73 Digital Multimeter 105-R0051 and Inductive Dwell-Tach-Volt-Ohms Tester 164-R0254 or equivalent to perform pinpoint tests. The Air Suspension System diagnostics require the use of Rotunda Super Star II Tester B or equivalent. COMPUTER CONTROLLED SUSPENSION

5 Page 5 of 29 Condition Possible Source Action Rear Suspension Does t Respond to Load Changes Rear Rides Low/High Unable to Enter Auto Test Poor Ride Quality Circuits. Compressor. Compressor air inlet tube. Air drier. Control module. Height sensor. Circuits. Control module. Spring solenoid valves. Height sensor. Super Star II Fault. Procedural error. Circuits. Control module. Air springs. Circuits. GO to Auto Test AA. GO to Auto Test AA. GO to Pinpoint Test S. GO to Auto Test AA. Air Suspension Warning Indicator ON Air suspension service switch OFF. CHECK switch in luggage compartment. Air suspension system concern. GO to Auto Test AA. Instrument cluster concern. GO to Section Pinpoint Tests PINPOINT TEST A: DTC 80 CONTROL MODULE DETECTS LOW BATTERY VOLTAGE A1 MEASURE SYSTEM VOLTAGE Disconnect control module connectors. Connect voltmeter between Pins C250, Circuit 1053 (LB/PK) and Pin C250, Circuit 57 (BK). Check the meter reading. Does the meter indicate between 0 and 11 volts? CHECK and SERVICE charging system. REFER to Section 14-00, then REPEAT Auto Test. GO to A2. A2 CHECK VOLTMETER READING Check the meter reading. Does the meter indicate at least 11 volts? GO to A3. GO to A1. A3 CHECK IGNITION SWITCH SENSE CIRCUIT Turn ignition switch to RUN. Measure voltage between Pin C250, Circuit 295 (LB/PK) and a good chassis ground. Meter should indicate battery voltage. Is there battery voltage?

6 Page 6 of 29 GO to A4. LOCATE and SERVICE open in Circuit 295 (LB/PK) or open Fuse 7 (15A). CHECK ignition switch. REFER to Section REPEAT Auto Test. A4 CHECK CONTROL MODULE GROUNDS Measure resistance between Pin C250, Circuit 57 (BK) and a good chassis ground. Meter should indicate less than 5 ohms. Does meter indicate less than 5 ohms? If DTC 80 was generated, REPLACE control module. REPEAT Auto Test. If unable to enter diagnostics with new control module, GO to Pinpoint Test S. SERVICE open in Circuit 57 (BK) or SERVICE ground terminals. REPEAT Auto Test. PINPOINT TEST B: DTC 72 DID NOT DETECT FOUR OPEN AND CLOSE DOOR SIGNALS B1 CHECK DOME LAMP OPERATION Open and close each door. Does dome lamp work properly from each door? GO to B2. REFER to Section for courtesy lamp diagnostics. B2 CHECK CONTROL MODULE INPUT Disconnect air suspension control module connectors C250 and C251. Using an ohmmeter, measure resistance between Pin C250 and Pin C250. Open drivers door. Is resistance less than 5 ohms? GO to B3. GO to B4. B3 CHECK CIRCUIT 344 (BK/Y) FOR SHORT TO GROUND Close all doors. Using an ohmmeter, measure resistance between C250 and Pin C250. Is resistance less than 5 ohms? SERVICE Circuit 344 (BK/Y) for short to ground. RESTORE vehicle. RETEST system. REPLACE control module. RESTORE vehicle. RETEST system. B4 CHECK CIRCUIT 344 (BK/Y) FOR OPEN Disconnect lighting control module connector C221. Using an ohmmeter, measure resistance of Circuit 344 (BK/Y) between lighting control module connector Pin C221 and air suspension control module connector Pin C250. Is resistance 5 ohms or less? REPLACE lighting control module. RESTORE vehicle. RETEST system. SERVICE Circuit 344 (BK/Y) for open. RESTORE vehicle. RETEST system. PINPOINT TEST C: DTC 39, 40 COMPRESSOR RELAY CONTROL CIRCUIT SHORT TO B+/GROUND

7 Page 7 of 29 C1 CHECK COMPRESSOR RELAY NOTE: The horn circuit and air suspension system use the same type of relay. Press horn pad to make sure horn is operating. Remove horn relay and install compressor relay in its place. Repeat Auto Test. Is DTC 39 or 40 displayed? INSTALL relays in original positions. Press horn button. If horn sounds, GO to C2 otherwise, REPLACE compressor relay and REPEAT Auto Test. INSTALL horn relay in original position. REPLACE compressor relay. REPEAT Auto Test. C2 CHECK FOR HARNESS SHORT Remove compressor relay from power distribution box. Turn air suspension switch ON. Measure voltage between Pins C251, Circuit 420 (DB/Y) and C250, Circuit 57 (BK). Does the meter indicate zero volts? GO to C3. GO to C4. C3 CHECK CIRCUIT 420 (DB/Y) FOR VOLTAGE Reinstall the compressor relay. Measure voltage between Pins C251, Circuit 420 (DB/Y) and C250, Circuit 57 (BK) on harness side of control module connectors. Does the meter indicate 0 volts? SERVICE Circuit 420 (DB/Y) for open or short. REPEAT Auto Test. GO to C5. C4 CHECK THE METER READING Check the meter reading. Does the meter indicate 12 volts? SERVICE short to B+ in Circuit 420 (DB/Y). REPEAT Auto Test. GO to C5.

8 Page 8 of 29 C5 CHECK POWER DISTRIBUTION BOX Reinstall the compressor relay in power distribution box. Measure voltage between Pins C251, Circuit 420 (DB/Y) and C250, Circuit 57 (BK) on harness side of control module connectors. Does the meter indicate 10 volts or more? REPLACE control module. REPEAT Auto Test. SERVICE power distribution box relay connector terminals. REPEAT Auto Test. PINPOINT TEST D: DTC 42 AIR SPRING SOLENOID VALVE SHORT TO GROUND D1 CHECK 30 AMP FUSE Remove and inspect power distribution box Fuse U (30A) for Circuit 1053 (LB/PK). Is fuse open? SERVICE short to ground in Circuit 1053 (LB/PK). REPLACE Fuse U (30A). NOTE: Circuit 1053 (LB/PK) feeds power to the spring solenoid valves, vent solenoid and compressor relay. CHECK for shorts at the compressor assembly. GO to D2. REPEAT Auto Test. D2 CHECK CIRCUIT 1114 (BR/PK) FOR SHORT TO GROUND Turn air suspension switch ON. Measure voltage between Pin C251, Circuit 1114 (BR/PK) and C250, Circuit 57 (BK). NOTE: If Pin C251, Circuit 1115 (T/W) or Pin C251, Circuit 1114 (BR/PK) is shorted to ground, the corresponding spring solenoid valve will always be open, even with the ignition switch OFF. Does the meter indicate 12 volts? GO to D4. GO to D3. D3 CHECK CIRCUIT 1114 (BR/PK) Measure resistance of Pin C251, Circuit 1114 (BR/PK) to ground. Is resistance 10 K ohms or less? SERVICE Circuit 1114 (BR/PK) for short to ground. SERVICE Circuit 1114 (BR/PK) for open. D4 CHECK CIRCUIT 1115 (T/W) FOR SHORT TO GROUND Measure voltage between Pins C251, Circuit 1115 (T/W) and C250, Circuit 57 (BK) of control module connectors. Does the meter indicate 12 volts?

9 Page 9 of 29 REPLACE control module. REPEAT Auto Test. SERVICE short to ground in Circuit 1115 (T/W) and/or Circuit 1114 (BR/PK). REPEAT Auto Test. PINPOINT TEST E: DTC 43 AIR SPRING SOLENOID VALVE SHORT TO BATTERY E1 CHECK LH AIR SPRING SOLENOID CIRCUIT NOTE: The resistance measurements in this procedure check the condition of the air spring solenoid valve coil. Remove Fuse U (30A) from power distribution box. Measure resistance between Pin C251, Circuit 1114 (BR/PK) and Pin C250, Circuit 1053 (LB/PK) on control module connectors. Meter should indicate 15 to 18 ohms. Are the meter readings as indicated above? Solenoid valve and wiring OK. GO to E2. SERVICE LH solenoid valve or wiring. E2 CHECK RH AIR SPRING SOLENOID VALVE CIRCUIT Measure resistance between Pins C251, Circuit 1115 (T/W) and C250, Circuit 1053 (LB/PK). Meter should indicate 15 to 18 ohms. Are the meter readings as indicated above? Solenoid valve and wiring OK. Go to E3. REPEAT Auto Test. SERVICE RH solenoid valve or wiring. REPEAT Auto Test. E3 CHECK FOR SHORT TO B+ AND REVERSED CIRCUITS Control module connectors C250 and C251 must be disconnected. Raise vehicle on hoist. Disconnect air spring solenoid valve connector C492 -LH, C467 -RH. Inspect connector to verify that Circuit 1053 (LB/PK) and 1115 (T/W) or 1053 (LB/PK) and 1114 (BR/PK) are not reversed in the connector. If circuits are reversed, install circuits in the correct terminals and repeat Auto Test.

10 Page 10 of 29 Measure voltage between C467 Circuit 1115 (T/W) and ground or C492 Circuit 1114 (BR/PK) and ground. Measure voltage between C467 or C492, Circuit 1053 (LB/PK) and ground. Meter should indicate B+ for Circuit 1053 (LB/PK) and 0 volts for Circuit 1114 (BR/PK). Are the meter readings as specified? REPLACE control modules. REPEAT Auto Test. SERVICE short to B+ in Circuit 1115 (T/W) and/or Circuit 1114 (BR/PK). REPEAT Auto Test. PINPOINT TEST F: DTC 44 VENT SOLENOID VALVE SHORT TO BATTERY F1 CHECK HARNESS CONNECTOR NOTE: The resistance measurements in this procedure check the condition of the vent solenoid valve coil and diode. A digital ohmmeter will not pass enough current through the diode to check its condition. Use Rotunda Inductive Dwell-Tach-Volt-Ohm Tester 164-R0254 or equivalent analog (needle-type) meter. Remove air cleaner intake tube and plastic shield protecting air compressor assembly as described. Disconnect air compressor connector C158. Inspect connector for obvious damage or corrosion. Make sure that wire terminals are located correctly and fully seated in connector. Circuit Circuit Function 421 (PK) Vent Solenoid Control 1053 (LB/PK) B+ Supply to Solenoid 538 (GY/R) B+ Supply from Compressor Relay 57 (BK) Ground Inspect air compressor assembly connector to make sure it is wired correctly and dry. Are harness connectors functional and dry? GO to F2. SERVICE as required. F2 CHECK HARNESS CIRCUIT 1053 (LB/PK) Disconnect compressor harness connector C158. Turn air suspension switch ON. Measure voltage between Circuit 1053 (LB/PK) and ground at compressor harness connector C158. Meter should indicate B+. Measure voltage between Circuit 421 (PK) and ground at compressor harness connector C158. Meter should indicate zero volts. Are the meter readings as specified? GO to F4. GO to F3. F3 CHECK THE METER

11 Page 11 of 29 Check the voltmeter readings. Are Circuits 1053 (LB/PK) and 421 (PK) at B+? SERVICE short to B+ in Circuit 421 (PK). REPEAT Auto Test. GO to F4. F4 CHECK RESISTANCE OF VENT SOLENOID Measure resistance between Terminals 1 and 2 on compressor assembly connector C158. Reverse leads and measure resistance again between Terminals 1 and 2. Meter should indicate ohms one way and less than 25 ohms the other way. Is the ohmmeter reading as specified? REPLACE control module. REPEAT Auto Test. RECHECK connector pins at compressor assembly for damage. If not OK, REPLACE compressor assembly. REPEAT Auto Test. If DTC 44 is repeated, REPLACE control module. REPEAT Auto Test. PINPOINT TEST G: DTC 45 SHORT IN VENT SOLENOID VALVE CIRCUIT G1 CHECK FUSE U (30A) Remove and inspect power distribution box Fuse U (30A). Is the fuse open? SERVICE short to ground in Circuit 1053 (LB/PK). REPEAT Auto Test. GO to G2. G2 CHECK CIRCUIT 420 (DB/Y) FOR SHORT TO GROUND NOTE: If Circuit 420 (DB/Y) (compressor) or 421 (PK) (vent solenoid valve) is shorted to ground, that component will always be ON, even with the ignition switch OFF. Turn air suspension switch ON. Measure voltage between Pins C251, Circuit 420 (DB/Y) and C250, Circuit 57 (BK) of control module connectors. Meter should indicate 12 volts. Does the meter indicate 12 volts? GO to G4. GO to G3. G3 CHECK RESISTANCE OF CIRCUIT 420 (DB/Y) Measure resistance of Pin C251, Circuit 420 (DB/Y) to ground.

12 Page 12 of 29 Is resistance 10K ohms or less? SERVICE Circuit 420 (DB/Y) for short to ground. SERVICE Circuit 420 (DB/Y) for open. G4 CHECK CIRCUIT 421 (PK) FOR SHORT TO GROUND Measure voltage between Pins C251, Circuit 421 (PK) and C250, Circuit 57 (BK) of control module connectors. Meter should indicate 12 volts. Does the meter indicate 12 volts? REPLACE control module. REPEAT Auto Test. GO to G5. G5 CHECK RESISTANCE OF CIRCUIT 421 (PK) TO GROUND Measure resistance of Pin C251, Circuit 420 (DB/Y) to ground. Is resistance 10K ohms or less? SERVICE short to ground in Circuit 420 (DB/Y) and/or Circuit 421 (PK). REPEAT Auto Test. If DTC 45 is repeated, REPLACE control module. REPEAT Auto Test. DRY any wet condition observed on solenoid vent connector and wiring harness. REPEAT Auto Test. PINPOINT TEST H: DTC 28 STEERING SELECT SWITCH NOT DETECTED H1 CHECK SELECT SWITCH INPUT Turn ignition switch OFF. Disconnect air suspension/evo control module connectors C250 and C251. Turn the select switch on the driver's left to the HIGH position. Turn the ignition switch to the RUN position. Using a voltmeter, measure voltage between Pin C250, Circuit 57 (BK) and Pin C251, Circuit 635 (Y). Is voltage 10 volts or more? GO to H2. SERVICE Circuit 635 (Y) for short to ground. REPEAT Auto Test. H2 CHECK CIRCUIT 635 (Y) Turn ignition switch to OFF position. Turn the select switch to the LOW position. Using an ohmmeter, measure resistance between Pin C250, Circuit 57 (BK) and Pin C251, Circuit 635 (Y). Is resistance 1 ohm or less? LEAVE ohmmeter connected. GO to H3. SERVICE Circuit 635 (Y) for open. REPEAT Auto Test. H3 CHECK SELECT SWITCH RESISTANCE Turn the select switch to the middle position. Measure the resistance between Pin C250, Circuit 57 (BK) and Pin C251, Circuit 635 (Y). Is resistance 10,000 ohms or greater? REPLACE control module. REPEAT Auto Test. REPLACE select switch. REPEAT Auto Test. PINPOINT TEST J: DTC 51 UNABLE TO DETECT LOWERING OF REAR

13 Page 13 of 29 J1 PERFORM FUNCTIONAL TEST NOTE: This test must be performed first and in a quiet environment. Perform Functional Test DTC 32. Refer to Functional Test. During Functional Test DTC 32, the vent solenoid valve located in compressor assembly should cycle ON and OFF repeatedly (one second ON, one second OFF) during the test. As the valve cycles, a clicking noise can be heard by listening at the front of the LH front wheel opening. Does valve cycle? GO to J11. GO to J2. J2 CHECK VENT SOLENOID VALVE CIRCUIT Remove air cleaner intake tube and air compressor plastic shield as described. Inspect compressor for obvious signs of water entry. Disconnect compressor connector C158. Inspect connector for corrosion or obvious damage. Make sure terminals are fully seated in connector. Measure voltage between Circuit 1053 (LB/PK) at harness connector C158 and a good chassis ground. Meter should indicate B+. Is there B+? GO to J3. SERVICE open in Circuit 1053 (LB/PK). REPEAT Auto Test. J3 CHECK HARNESS Measure voltage between Circuit 421 (PK) in harness connector C158 and a good chassis ground. Meter should pulse between 0 volts and B+ (during Functional Test 32). Does voltage pulse? REPLACE compressor assembly. REPEAT Auto Test. GO to J4. J4 CHECK CIRCUIT 421 (PK) FOR OPEN Measure resistance on Circuit 421 (PK) between compressor connector and Pin C251, Circuit 421 (PK) of control module connector. Meter should indicate less than 10 ohms. Is resistance less than 10 ohms? Black Connector C251

14 Page 14 of 29 GO to J5. SERVICE open in Circuit 421 (PK). REPEAT Auto Test. J5 CHECK AIR SPRING SOLENOID VALVES Enter Functional Test DTC 33. Leave air suspension switch ON and raise vehicle on hoist. Feel each spring solenoid valve to check for ON and OFF cycling. A clicking noise will be heard when they cycle, but each solenoid valve must be felt to make sure both are operating. Are both valves cycling? GO to J9. DO NOT EXIT Functional Test 33. GO to J6. J6 CHECK AIR SPRING SOLENOID VALVE HARNESS AND CONTROL MODULE Disconnect inoperative air spring solenoid valve connector C492 -LH, C467 -RH. Measure voltage between both circuits in solenoid valve connector. Meter should pulse between 0 volts and B+. Are there voltage pulses? REPLACE inoperative air spring solenoid valve. REPEAT Auto Test. EXIT Functional Test 33. GO to J7. J7 CHECK AIR SPRING SOLENOID VALVE BATTERY FEED CIRCUIT 1053 (LB/PK) Measure voltage between Circuit 1053 (LB/PK) at air spring solenoid valve connector C492 -LH, C467 -RH and a good chassis ground. Meter should indicate B+. Is there 11 volts or more? GO to J8. SERVICE open in Circuit 1053 (LB/PK). REPEAT Auto Test. J8 CHECK SPRING SOLENOID VALVE CONTROL CIRCUITS Measure resistance of Circuit 1114 (BR/PK) between solenoid valve connector C492 and Pin C251. Measure resistance of solenoid Circuit 1115 (T/W) between solenoid valve connector C467 and Pin C251, as shown. Is resistance less than 10 ohms?

15 Page 15 of 29 GO to J9. SERVICE open in Circuit between control module and solenoid valve connector. REPEAT Auto Test. J9 CHECK LH AIR SPRING SOLENOID CIRCUITS NOTE: The resistance measurements in this procedure check the condition of the air spring solenoid valve coil. Remove Fuse U (30A) from power distribution box. Measure resistance between Pins C251, Circuit 1114 (BR/PK) and C250, Circuit 1053 (LB/PK) (checking LH). Meter should indicate 15 to 18 ohms. Is the meter reading for the solenoid valve as specified? GO to J10. REPLACE damaged spring solenoid valve. REPEAT Auto Test. J10 CHECK RH AIR SPRING SOLENOID CIRCUITS Measure resistance between Pins C251, Circuit 1115 (T/W) and C250, Circuit 1053 (LB/PK). Meter should indicate 15 to 18 ohms. Is the meter reading as specified for the solenoid valve? REPLACE control module. REPEAT Auto Test. REPLACE damaged spring solenoid valve. REPEAT Auto Test. J11 CHECK HEIGHT SENSOR INSTALLATION

16 Page 16 of 29 Leave Star Tester in Functional Test mode, but do not select a Function Test (Star Tester button should be pressed down). Leave air suspension switch ON. Making sure that Star tester is accessible, raise vehicle on hoist. Check that air suspension height sensor is attached to both ball studs. Check upper and lower air suspension height sensor mounting brackets for obvious damage. Are air suspension height sensor attachments OK? GO to J13. SERVICE as necessary. GO to J12. J12 CHECK BALL STUDS Check upper and lower height sensor ball studs. Make sure height sensors fit tightly and go all the way on. Do height sensors fit ball studs properly? GO to J14. REPLACE ball studs. REFER to Section for rear suspension service. LOWER vehicle. REPEAT Auto Test. J13 CHECK AIR FLOW THROUGH SPRING SOLENOID VALVES CAUTION: Rear of vehicle must be supported by frame. If rear is supported by axle, rear of vehicle will lower during this test. NOTE: Some air must be in each air rear spring to perform this test. Disconnect air lines at both spring solenoid valves. Remove air spring solenoid heat shields, if equipped. Enter Functional Test DTC 33 to cycle air spring solenoid valve. Refer to Auto Test. Does air flow from each air spring solenoid valve when it is cycled open? EXIT Functional Test 33. CONNECT solenoid valve air lines and heat shields. GO to J14. REPLACE inoperative spring solenoid valve. RESUME Function Test 33. If a solenoid does not release air, GO to J6. J14 CHECK FOR ADEQUATE SPRING PRESSURE Lower vehicle. There should be nothing supporting vehicle except the wheels. Cycle ignition switch (RUN-OFF-RUN), then open and close driver side door to start automatic trim height adjustment. Allow vehicle to establish automatic trim height. Measure distance between center of rear wheel lip opening and bottom of wheel (not bottom of tire). Measurement should be a minimum of mm (24-25 inch). This is vehicle trim height. Is the vehicle higher? GO to J15. GO to J13. J15 CHECK FOR VEHICLE LOW Measurement should be a minimum of mm (24-25 inch). This is vehicle trim height. Is the vehicle low? GO to J17. GO to J16. J16 CHECK AIR FLOW THROUGH LINES CAUTION: Rear of vehicle may drop rapidly once Functional Test DTC 23 is entered. Dropping rear of vehicle too low could damage vehicle or components. Remove air cleaner intake tube and plastic shield from compressor assembly as described. Disconnect air line at compressor air drier.

17 Page 17 of 29 Enter Functional Test DTC 23 vent rear. Refer to Functional Tests. Air should flow from disconnected air line and vehicle should drop about 25.4 mm (1.0 inch) in seconds. Does the air flow from air line and vehicle drop? EXIT Functional Test 23 before rear of vehicle becomes too low. GO to J18. GO to J17. J17 CHECK AIR FLOW THROUGH LINES Check air flow through lines. Is there little or no air flowing, vehicle does not lower or lowers very slowly? SERVICE air line from compressor to solenoid valves for blockage or kinks. REPEAT Auto Test. GO to J18. J18 CHECK AIR FLOW THROUGH COMPRESSOR AIR DRIER Remove compressor air drier from compressor as described. Connect air line to compressor air drier. Enter Functional Test DTC 23 vent rear. Is there little or no air flow through compressor air drier? REPLACE compressor air drier. INSTALL compressor assembly. REPEAT Auto Test. REPLACE air compressor assembly. REPEAT Auto Test. PINPOINT TEST K: DTC 54 UNABLE TO DETECT RAISING OF REAR K1 PERFORM COMPRESSOR FUNCTIONAL TEST Enter Functional DTC Test 31 compressor relay toggle. Refer to Auto Test then Functional Test. Compressor should cycle ON and OFF repeatedly (one second ON, one second OFF) during this test. Cycling of the compressor can be heard from the LH front wheel well. Does compressor cycle? GO to K15. DO NOT EXIT Functional Test DTC 31. GO to K2. K2 MEASURE VOLTAGE AT COMPRESSOR Remove air cleaner intake tube and compressor plastic shield as described. Disconnect compressor connector C158. Measure voltage between Circuits 538 (GY/R) and Circuit 57 (BK) of connector C158. Meter should pulse between B+ and 0 volts (during Functional Test 31). Does the meter pulse between B+ and zero volts? CONNECT compressor connector. WAIT 10 minutes for compressor internal circuit breaker to cool down and close. Circuit breaker may have opened due to excessive compressor run-time during diagnostics. If compressor does not start to cycle on and off after 10 minutes, REPLACE compressor. REPEAT Auto Test. DO NOT EXIT Functional Test DTC 31. GO to K3. K3 CHECK COMPRESSOR RELAY Relay should cycle ON and OFF (one second ON, one second OFF) during this test. As the relay cycles a clicking noise will be heard. Does relay cycle? GO to K7. GO to K4.

18 Page 18 of 29 K4 CHECK COMPRESSOR RELAY REPLACEMENT The horn circuit and the air suspension system use the same type of relay. Press horn pad to make sure horn is operating. Remove relay and install horn relay in its place. Repeat Auto Test. Is DTC 54 displayed? INSTALL relays in original positions. GO to K5. INSTALL horn relay in original position. REPLACE compressor relay. REPEAT Auto Test. K5 CHECK RELAY BATTERY FEED CIRCUIT Measure voltage between Circuit 1053 (LB/BK) at relay terminal and a good chassis ground. Meter should indicate B+. Is there 10 volts or more? GO to K6. SERVICE Circuit 1053 (LB/BK) for open. REPEAT Auto Test. K6 CHECK RELAY CONTROL CIRCUIT 420 (DB/Y) Measure resistance of Circuit 420 (DB/Y) between power distribution box and Pin C251, Circuit 420 (DB/Y). Meter should indicate less than 5 ohms. Is resistance less than 5 ohms? GO to K7. SERVICE open in Circuit 420 (DB/Y). REPEAT Auto Test. K7 CHECK B+ SUPPLY CIRCUIT Remove air compressor relay from power distribution box. Disconnect air compressor connector C158. Measure resistance of Circuit 538 (GY/R) between power distribution box and compressor connector C158. Resistance should be less than 5 ohms. Is resistance less than 5 ohms?

19 Page 19 of 29 GO to K8. SERVICE open in Circuit 538 (GY/R). REPEAT Auto Test. K8 CHECK GROUND CIRCUIT 57 (BK) Measure resistance between Circuit 57 (BK) at compressor connector C158 and a good chassis ground. Meter should indicate less than 5 ohms. Is resistance less than 5 ohms? GO to K9. SERVICE open in Circuit 57 (BK). REPEAT Auto Test. K9 CHECK AIR SPRING SOLENOID VALVES Enter Functional Test DTC 33. Refer to Pinpoint Test AB. Leave air suspension switch ON and raise vehicle on hoist. Feel both spring solenoid valves to see if they are cycling ON and OFF. A clicking noise will be heard when they cycle, but each solenoid valve must be felt to make sure that both are operating. Are both solenoid valves cycling? GO to K15. DO NOT EXIT Functional Test 33. GO to K10. K10 CHECK AIR SPRING SOLENOID VALVE HARNESS AND CONTROL MODULE CIRCUITS Disconnect inoperative spring solenoid valve connector C467 -RH, C492 -LH. Measure voltage between both circuits in connector. Meter should pulse between 0 volts and B+. Are there meter pulses? REPLACE inoperative spring solenoid valve. REPEAT Auto Test. EXIT Functional Test 33. GO to K11. K11 CHECK AIR SPRING SOLENOID VALVE BATTERY FEED CIRCUIT Measure voltage between Circuit 1053 (LB/PK) circuit at spring solenoid valve connector C467 -RH, C492 -LH and a good chassis ground. Meter should indicate B+. Is there 11 volts or more?

20 Page 20 of 29 GO to K12. SERVICE open in Circuit 1053 (LB/PK). REPEAT Auto Test. K12 CHECK CONTINUITY OF SPRING SOLENOID VALVE CONTROL CIRCUITS Measure resistance of spring solenoid valve control circuit between solenoid valve connector C492 -LH, C467 -RH and control module connector C251. Is resistance less than 3 ohms? GO to K13. SERVICE open in circuit between control module and solenoid valve connector. REPEAT Auto Test. K13 CHECK LH AIR SPRING SOLENOID CIRCUITS Remove power distribution box Fuse U (30A). Measure resistance between Pins C251, Circuit 1114 (BR/PK) and C250, Circuit 1053 (LB/PK) on control module connectors (checking LH). Meter should indicate 15 to 18 ohms. Is the meter reading as specified? GO to K14. REPLACE damaged spring solenoid valve. REPEAT Auto Test. K14 CHECK RH AIR SPRING SOLENOID VALVE CIRCUIT Measure resistance between Pins C251, Circuit 1115 (T/W) and C250, Circuit 1053 (LB/PK).

21 Page 21 of 29 Meter should indicate 15 to 18 ohms. Is the meter reading for the spring solenoid valve as specified? REPLACE control module. REPEAT Auto Test. REPLACE damaged spring solenoid valve. REPEAT Auto Test. K15 CHECK HEIGHT SENSOR INSTALLATION Leave Star Tester in Functional Test mode, but do not select a Functional Test (Star tester button should be pressed down). Leave air suspension switch ON. Raise vehicle on hoist. Check that air suspension height sensor is attached to both ball studs. Check that upper and lower mounting brackets are not bent or damaged. Are air suspension height sensor attachments OK? GO to K21. GO to K16. K16 INSPECTION OF HEIGHT SENSOR FITTED TO BALL STUDS Check upper and lower air suspension height sensor mounting brackets for obvious damage. Are one or both ends off ball studs? PUSH air suspension height sensor onto ball studs. MAKE SURE air suspension height sensor fits securely on both ball studs. If not, REPLACE air suspension height sensor. LOWER vehicle. REPEAT Auto Test. GO to K17. K17 CHECK HEIGHT SENSOR MOUNTING BRACKETS FOR DAMAGE Check upper and lower air suspension height sensor mounting brackets for obvious damage. Are the air suspension height sensor attachments bent or damaged? SERVICE brackets. LOWER vehicle. REPEAT Auto Test. GO to K18. K18 CHECK FOR AIR FLOW FROM AIR COMPRESSOR CAUTION: Support rear of vehicle on frame. If rear of vehicle is supported by axle, air springs will be damaged during this test. Lower and support rear of vehicle. Disconnect air line from compressor air drier. Enter Functional Test 26 compress rear. Air should flow from compressor air drier while compressor is running. Does the air flow from compressor air drier? EXIT Functional Test 26. CONNECT air line to compressor air drier. GO to K20. GO to K19.

22 Page 22 of 29 K19 CHECK AIR COMPRESSOR AIR FLOW Check for restriction in compressor air inlet tube. Disconnect inlet tube from air compressor. Does air flow from compressor air drier? SERVICE air inlet tube. REPEAT Auto Test. EXIT Functional Test 26. GO to K20. K20 CHECK AIR FLOW WITH COMPRESSOR AIR DRIER REMOVED Remove compressor air drier from air compressor as described. Enter Functional Test DTC 26 compress rear. Air should flow from compressor air drier fitting on compressor while compressor is running. Does the air flow from compressor air drier fitting? REPLACE compressor air drier. REPLACE compressor assembly. CAUTION: Enter Functional Test DTC 26 as described in Functional Test Procedure and fill air springs for about 90 seconds before lowering rear of vehicle to prevent damage to vehicle and components. REPEAT Auto Test. CAUTION: Enter Functional Test DTC 26 as described in Functional Test Procedure and fill air springs for about 90 seconds before lowering rear of vehicle to prevent damage to vehicle and components. REPEAT Auto Test. K21 CHECK FOR AIR LEAKS IN LINES AND SPRINGS NOTE: Support rear of vehicle on frame, not on axle. Supporting vehicle by the frame allows full extension of air rear springs for leak detection. Raise rear of vehicle. Enter Functional Test DTC 26 compress rear. Refer to Functional Test Procedure. Check air lines and air rear springs for leaks. NOTE: The air lines are routed along the LH rocker panel along with the fuel and brake lines. Are leaks detected? EXIT Functional Test DTC 26. SERVICE leaks in air lines and REPLACE rear spring (s). REPEAT Auto Test. GO to K22. K22 CHECK VENT SOLENOID Check for air leaking from vent solenoid. Does air escape from vent solenoid when compressor is running? REPLACE compressor assembly. REPEAT Auto Test. GO to K23. K23 CHECK FOR BLOCKED AIR LINES Disconnect air lines at both solenoid valves. Remove air spring solenoid heat shields, if equipped. Support rear of vehicle on frame to prevent vehicle from lowering during functional test. Enter Functional Test DTC 26 compress rear. Air should flow from both air lines and from both solenoid valves. Does air flow from both air lines and from both air spring solenoid valves? REPLACE control module. REPEAT Auto Test. GO to K24. K24 CHECK FOR NO AIR FLOW FROM REAR AIR SPRING(S) Check air flow. Is there air flow from rear spring(s)? SERVICE blocked air lines. REPEAT Auto Test. SERVICE air spring solenoids. REPEAT Auto Test. PINPOINT TEST L: DTC 68 SHORT IN REAR AIR SUSPENSION HEIGHT SENSOR CIRCUIT

23 Page 23 of 29 L1 CHECK FOR DTC 71 Disconnect rear air suspension height sensor electrical connector C468. Turn air suspension switch ON. Perform Auto Test. Is DTC 71 displayed? REPLACE air suspension height sensor. REPEAT Auto Test. GO to L2. L2 CHECK FOR DTC 68 Check the display for DTC 68. Is DTC 68 displayed? GO to L3. GO to L1. L3 CHECK CIRCUIT 428 (O/BK) FOR SHORT TO GROUND Measure resistance between Pins C250, Circuit 57 (BK) and C250, Circuit 428 (O/BK). Meter should indicate more than 10,000 ohms. Is resistance more than 10,000 ohms? GO to L4. SERVICE Circuit 428 (O/BK) for short to ground. GO to L4 before servicing short in Circuit 428 (O/BK). L4 CHECK CIRCUIT 427 (PK/BK) FOR SHORT TO GROUND Measure resistance between Pins C250, Circuit 57 (BK) and C250, Circuit 427 (PK/BK) Meter should indicate more than 10,000 ohms. Does the meter indicate more than 10,000 ohms? Gray Connector C250 REPLACE control module. REPEAT Auto Test. SERVICE short to ground in Circuit 427 (PK/BK). REPEAT Auto Test. PINPOINT TEST M: DTC 46 AIR SUSPENSION HEIGHT SENSOR SUPPLY CIRCUIT SHORTED

24 Page 24 of 29 M1 CHECK SENSOR Raise vehicle on hoist. Disconnect air suspension height sensor electrical connector. Lower vehicle. Turn air suspension switch ON. Perform Auto Test. Ignore all DTCs except DTC 46. Is DTC 46 received? GO to M2. REPLACE air suspension height sensor. REPEAT Auto Test. If DTC 46 is again received, REPLACE control module. REPEAT Auto Test. M2 CHECK CIRCUIT 429 (P/LG) FOR SHORT TO BATTERY Turn air suspension switch ON. Measure voltage between Pins C251, Circuit 429 (P/LG) and C250, Circuit 57 (BK). Meter should indicate 0 volts. Does the meter indicate 0 volts? GO to M3. SERVICE short to B+ in Circuit 429 (P/LG). REPEAT Auto Test. M3 CHECK CIRCUIT 429 (P/LG) FOR SHORT TO GROUND Measure resistance between Pins C251, Circuit 429 (P/LG) and C250, Circuit 57 (BK). Meter should indicate greater than 10,000 ohms. Does meter read more than 10,000 ohms? REPLACE control module. REPEAT Auto Test. SERVICE short to ground in Circuit 429 (P/LG). REPEAT Auto Test. PINPOINT TEST N: DTC 71 AIR SUSPENSION HEIGHT SENSOR CIRCUIT OPEN N1 VISUAL INSPECTION NOTE: If the control module is not in the functional test mode, the voltages in the following test steps will be incorrect. Turn ignition switch to RUN. Turn air suspension switch ON. Enter Functional Test mode. Refer to Functional Test Procedure. DO NOT select a Functional Test at this time. Star tester button should remain in TEST (down) position. Raise vehicle on hoist. Verify air suspension height sensor electrical connector C468 is connected and connector and wiring have no obvious damage. Are connector and wiring worn or damaged?

25 Page 25 of 29 SERVICE connector and wiring as necessary. REPEAT Auto Test. GO to N2. N2 CHECK CIRCUITS 427 (PK/BK) AND 428 (O/BK) Disconnect air suspension height sensor C468. Measure voltage between Circuit 427 (PK/BK) and Circuit 428 (O/BK) and a good chassis ground. Meter should indicate 4 volts for each circuit. Does the meter indicate 4 volts for each circuit? GO to N4. GO to N3. N3 ISOLATE OPEN IN CIRCUIT 427 (PK/BK), CIRCUIT 428 (O/BK) OR CONTROL MODULE Measure resistance between air suspension height sensor connector C468 and control module connector Pin C250, Circuit 428 (O/BK). Measure resistance of connector Pin C250, Circuit 427 (PK/BK) to C468. Resistance should be less than 10 ohms. Is resistance less than 10 ohms? REPLACE control module. REPEAT Auto Test. LOCATE and SERVICE open in Circuit 427 (PK/BK) or Circuit 428 (O/BK). REPEAT Auto Test. N4 CHECK CIRCUIT 432 (BK/PK) Measure resistance in Circuit 432 (BK/PK) between air suspension height sensor connector C468 and a good ground. Meter should indicate less than 10 ohms. Is resistance less than 10 ohms? GO to N6. GO to N5. N5 ISOLATE OPEN IN CIRCUIT 432 (BK/PK) OR CONTROL MODULE Measure resistance of Circuit 432 (BK/PK) between the air suspension height sensor connector C468 and control module connector Pin C251, Circuit 432 (BK/PK). Resistance should be less than 10 ohms.

26 Page 26 of 29 Is resistance less than 10 ohms? REPLACE control module. REPEAT Auto Test. LOCATE and SERVICE open in Circuit 432 (BK/PK). REPEAT Auto Test. N6 CHECK CIRCUIT 429 (P/LG) Measure voltage between connector C468, Circuit 429 (P/LG) and a good chassis ground. Meter should pulse between 4 and 6 volts. Does the meter pulse between 4 and 6 volts? Circuit 429 (P/LG) OK, REPEAT Auto Test. GO to N7. N7 ISOLATE OPEN IN CIRCUIT 429 (P/LG) OR CONTROL MODULE Measure resistance of Circuit 429 (P/LG) between air suspension height sensor connector C468 and control module connector Pin C251, Circuit 429 (P/LG). Resistance should be less than 10 ohms. Is resistance less than 10 ohms? REPLACE control module. REPEAT Auto Test. LOCATE and SERVICE open in Circuit 429 (P/LG). REPEAT Auto Test. PINPOINT TEST P: DTC 55 SPEED GREATER THAN 15 MPH NOT DETECTED P1 CHECK SPEEDOMETER OPERATION Test drive vehicle. Did speedometer record speed over 24 Km/h (15 mph) during last ignition cycle? GO to P2. REFER to Section P2 CHECK CIRCUIT 679 (GY/BK) Disconnect air suspension control module connector C250. Disconnect vehicle speed sensor connector C1020. Using an ohmmeter, measure resistance of Circuit 679 (GY/BK) between air suspension control module connector Pin C250 and vehicle speed sensor connector C1020. Is resistance 5 ohms or less?

27 Page 27 of 29 GO to P3. SERVICE Circuit 679 (GY/BK) for open. RESTORE vehicle. RETEST system. P3 CHECK CIRCUIT 676 (PK/O) Using an ohmmeter, measure resistance of Circuit 676 (PK/O) between air suspension control module connector Pin C250 and vehicle speed sensor connector C1020. Is resistance 5 ohms or less? REPLACE air suspension control module. RESTORE vehicle. RETEST system. SERVICE Circuit 676 (PK/O) for open. RESTORE vehicle. RETEST system. PINPOINT TEST Q: DTC 60 SERVICE SWITCH SHORTED TO BATTERY Q1 CHECK CIRCUIT 429 (P/LG) Disconnect air suspension service switch connector C458. Using a voltmeter connected to ground, measure voltage at Circuit 429 (P/LG) at air suspension service switch connector C458. Is voltage B+? SERVICE Circuit 429 (P/LG) for short to B+. RESTORE vehicle. RETEST system. GO to Q2. Q2 CHECK CIRCUIT 418 (DG/Y) Using a voltmeter connected to ground, measure voltage at Circuit 418 (DG/Y) at air suspension service switch connector C458. Is voltage B+? SERVICE Circuit 418 (DG/Y) for short to ground. RESTORE vehicle. RETEST system. REPLACE air suspension control module. RESTORE vehicle. RETEST system. PINPOINT TEST R: DTC 61 SERVICE SWITCH SHORTED TO GROUND OR OPEN R1 CHECK CIRCUIT 429 (P/LG) Disconnect air suspension service switch connector C458. Using an ohmmeter connected to ground, measure resistance of Circuit 429 (P/LG) at air suspension service switch connector C458. Is resistance less than 500 ohms? SERVICE Circuit 429 (P/LG) for short to ground. RESTORE vehicle. RETEST system. GO to R2. R2 CHECK CIRCUIT 418 (DG/Y) Using an ohmmeter connected to ground, measure resistance of Circuit 418 (DG/Y) at air suspension service switch connector. Is resistance less than 500 ohms? GO to R3. REPLACE air suspension service switch. RESTORE vehicle. RETEST system. R3 CHECK FOR SHORTED CONTROL MODULE Disconnect air suspension control module connector C250. Using an ohmmeter connected to ground, measure resistance of Circuit 418 (DG/Y) at air suspension service switch connector C458. Is resistance less than 10K ohms? SERVICE Circuit 418 (DG/Y) for short to ground. RESTORE vehicle. RETEST system. GO to R4. R4 CHECK FOR OPEN CIRCUIT OR SWITCH Reconnect service switch.