On Board Diagnostics II A PCED

1998 PCED On Board Diagnostics II A SECTION 5A: Pinpoint Tests HA: Natural Gas Fuel Control HA: Introduction HA30 DTCS P05, P0141, P0155 AND P0161: HO2S HEATER SIGNAL CIRCUIT IS OPEN, SHORTED TO GROUND, SHORTED TO VPWR OR EXCESSIVE CURRENT DRAW Diagnostic Trouble Codes (DTCs) P05, P0141, P0155 and P0161 indicate a short to ground, or open, or short to VPWR in the HO2S heater circuit. DTC/HO2S Reference List DTC P05 = HO2S HTR-11 DTC P0141 = HO2S HTR-12 DTC P0155 = HO2S HTR-21 DTC P0161 = HO2S HTR-22 Possible causes. Shorts to VPWR in harness or HO2S. Water in connectors. Cut or pulled wires. Disconnected wiring. Open VPWR circuit. Open GND circuit. Low battery voltage. Corrosion or poor mating terminals. Damaged PCM. te: On some applications, a vehicle hoist is required to access the HO2S harness. Visually inspect the HO2S circuit for exposed wiring, contamination, corrosion and proper installation. Were any concerns found during the visual inspection? REPAIR any concerns found in the visual inspection. RESTORE vehicle. RERUN Quick Test. GO to HA31. HA31 PERFORM KOEO SELF-TEST Key on. Engine at 2000 rpm for 5 minutes. Activate key on, engine off (KOEO) Self-Test. Are DTCs P05, P0141, P0155 and/or P0161 present? GO to HA32. DTCs present. Fault may be intermittent. GO to Pinpoint Test Step Z1 with the following data: HO2S PIDs and a list of Possible causes. HA32 CHECK VPWR VOLTAGE TO HO2S HARNESS CONNECTOR te: If DTCs P05 and P0155 or P0141 and P0161 are displayed, both heater circuits will require testing. DTCs displayed separately are tested individually. Disconnect the appropriate HO2S(s). Measure voltage between VPWR circuit and SIG RTN circuit at the HO2S harness connector (refer to schematic at the beginning of this Pinpoint Test). Is the voltage greater than 10.5 volts? GO to HA34. GO to HA33. HA33 CHECK VPWR CIRCUIT FOR OPEN IN HARNESS Install breakout box, PCM disconnected. Measure resistance of the VPWR circuit between PCM Test Pins 71 (VPWR) and VPWR circuit at the HO2S harness connector. Is the resistance less than 4.0 ohms? GO to HA34. CHECK fuse in circuit. If fuse is OK, REPAIR open circuit. RESTORE vehicle. RERUN Quick Test.

HA34 CHECK HO2S HEATER RESISTANCE Measure the resistance (refer to schematic at the beginning of this pinpoint test). Is the resistance between 3 and 30 ohms? GO to HA35. REPLACE HO2S. RESTORE vehicle. RERUN Quick Test. HA35 CHECK HO2S CASE FOR SHORT TO VPWR AND HEATER GND Measure resistance between the HO2S Heater GND at the HO2S connector and the HO2S case. Measure resistance between the HO2S VPWR at the HO2S sensor connector and the HO2S sensor case (refer to the schematic at the beginning of this pinpoint test). Is the resistance greater than 10,000 ohms? GO to HA36. REPLACE HO2S. RESTORE vehicle. RERUN Quick Test. HA36 CHECK FOR SHORTS TO OTHER GROUNDS AND VPWR IN THE HO2S HEATER GROUND HARNESS CIRCUITS Disconnect Scan Tool from DLC. Use the following list to measure the resistance between the appropriate test pins at the breakout box: DTC P05 = HO2S HTR-11 (HTR GND) PCM Test Pin 93 and PCM test pins 24, 103, 91 and 71. DTC P0141 = HO2S HTR-12 (HTR GND) PCM test pin 95 and PCM Test Pins 24, 103, 91 and 71. DTC P0155 = HO2S HTR-21 (HTR GND) PCM test pin 94 and PCM test pins 24, 103, 91 and 71. DTC P0161 = HO2S HTR-22 (HTR GND) PCM test pin 96 and PCM test pins 24, 103, 91 and 71. Is the resistance greater than 10,000 ohms? GO to HA37. REPAIR shorted circuit. RESTORE vehicle. RERUN Quick Test. HA37 CHECK HO2S HEATER GROUND FOR OPEN IN HARNESS Use the following list to measure resistance between the appropriate PCM test pins and the HO2S HTR GND at the harness connector: HO2S HTR-11 Test Pin 93 (HTR GND) HO2S HTR-12 Test Pin 95 (HTR GND) HO2S HTR-21 Test Pin 94 (HTR GND) HO2S HTR-22 Test Pin 96 (HTR GND) Is the resistance less than 4.0 ohms? Open or shorted or excessive resistance in the heater circuit in the PCM. REPLACE PCM. RESTORE vehicle. RERUN Quick Test. REPAIR open or excessive resistance in the heater circuit in harness. RESTORE vehicle. RERUN Quick Test. HA40 DTC P11, P1151, P12 AND P1152: UPSTREAM HO2S(S) NOT SWITCHING. DTCs P10 AND P1150: FUEL SYSTEM NOT SWITCHING AT THE FUEL TRIM (RICH OR LEAN) Diagnostic Trouble Codes (DTCs) P11 bank 1 (Cylinder 1) and P1151 bank 2 indicate the fuel/air ratio is correcting rich for an overly lean condition. The HO2S voltage is less than 0.45 volt. DTCs P12 bank 1 (Cylinder 1) and P1152 bank 2 indicate the fuel/air ratio is correcting lean for an overly rich condition. The HO2S voltage is greater than 0.45 volt. DTCs P10 and P1150 indicate the fuel control system has reached its maximum compensation for lean or rich condition and the HO2S is not switching. HO2S DTCs Reference list HO2S-11 = DTCs P11, P12 and P10 HO2S-21 = DTCs P1151, P1152 and P1150 Fuel system Excessive fuel pressure. Leaking fuel injector(s). Leaking fuel pressure regulator. Low fuel pressure. Contaminated fuel injector(s). Ignition system Spark plugs. Spark plug wires.

Coil(s). Induction system Air leaks after the MAF sensor assembly. Vacuum leaks. Restricted air inlet. PCV system. Improperly seated engine oil dipstick. Base engine Oil overfill. Cam timing. Cylinder compression. Exhaust leaks before or near the HO2S(s). Check intake air system for leaks, obstructions, damage and blockage. Verify integrity of the PCV system. Check for disconnected spark plug wires. Check for vacuum leaks. Are any of the above concerns present? REPAIR as necessary. RERUN Quick Test. GO to HA42. HA41 DTCs P0172, P0174, P0171 AND P0175: FUEL SYSTEM AT THE CORRECTED FUEL TRIM Diagnostic Trouble Codes (DTCs) P0171 bank 1 (Cylinder 1) and DTC P0174 bank 2 indicate the fuel/air ratio is too lean. The fuel trim system is at the rich correction limit. DTC P0172 bank 1 and DTC P0175 bank 2 indicate the fuel/air ratio is too rich. The fuel trim system is at the lean correction limit. HO2S DTCs Reference list: HO2S-11 = DTCs P0171 and P0172 HO2S-21 = DTCs P0174 and P0175 Fuel system Excessive fuel pressure. Leaking fuel injector(s). High fuel pressure. Low fuel pressure. Contaminated fuel injector(s) Ignition system Spark plugs. Spark plug wires. Coils. Induction system Air leaks after the MAF sensor assembly. Vacuum leaks. Restricted air inlet. PCV system. Improperly seated engine oil dipstick. Base engine Oil overfill. Cam timing. Cylinder compression. Exhaust leaks before or near the HO2S(s). Check intake air system for leaks, obstructions and damage. Check air cleaner element, air cleaner housing for blockage. Verify fuel level. Verify integrity of the PCV system. Check for disconnected spark plug wires. Check for vacuum leaks. Verify customer did not run out of fuel. Are any of the above concerns present? REPAIR as necessary. RERUN Quick Test. GO to Pinpoint Test Step DC25. If MAF reading is within specification, return to Pinpoint Test Step HA42. HA42 PERFORM KOER SELF-TEST

Enter Key On Engine Running (KOER) Self-Test. Are HO2S DTCs P11, P12, P1151 or P1152 present? For DTCs P10, P1150 P0171, P0174, P0172 and P0175: GO to HA43. GO to HA43. All others: The fault that produced the DTC is intermittent. GO to Pinpoint Test Step Z1 with the following data: HO2S-11, 21, 12, 22 PIDs and list of Possible causes. HA43 CHECK FUEL PRESSURE WARNING: THE FUEL SYSTEM IS PRESSURIZED WHEN THE ENGINE IS NOT RUNNING. TO PREVENT INJURY OR FIRE, USE CAUTION WHEN WORKING ON THE FUEL SYSTEM. BECOME FAMILIAR WITH THE WARNING, CAUTION AND NOTE IN PINPOINT TEST HB BEFORE SERVICING. te: Fuel rail pressure gauge is part of the NG Special Rotunda Tool Kit 4-00114. NG fuel pressure gauge connected at the fuel rail Schrader valve. Access FRP PID and monitor both gauge and PID. Record pressure readings. Key on, engine on. Record pressure readings. Increase engine speed to 2500 rpm and maintain for one minute. Record pressure reading. Are the fuel pressure readings between 552 or 827 kpa (80-120 psi)? Fuel system is capable of required pressure. GO to HA44. Fuel pressure out of specification. GO to Pinpoint Test HB1. HA44 CHECK FUEL SYSTEM FOR PRESSURE STABILITY Cycle key on and off twice. Verify there are no external leaks (service as necessary). Does the fuel pressure remain within 69 kpa (10 psi) of the highest reading after two minutes? For DTCs P10, P1150, P0171, P0172, P0174 and P0175: GO to HA45. For Starts: GO to HA45. Excessive pressure loss. GO to Pinpoint Test Step HB1. All other DTCs: GO to HA62. HA45 CHECK FUEL SYSTEM FOR PRESSURE STABILITY WITH KEY ON Access and monitor FRP sensor PID. Key On, Engine Off. Monitor fuel pressure gauge. Does the fuel pressure remain within 69 kpa (10 psi) of the highest reading after 10 seconds? For Starts: GO to HA46. For DTCs P10, P1150, P0171 and P0174: For DTCs P0172 and P0175: GO to HA57. GO to HA56. HA46 CHECK FUEL INJECTOR(S) ABILITY TO DELIVER FUEL Access and monitor FRP sensor PID. Cycle key twice. Locate and disconnect the inertia fuel shutoff (IFS) switch. Crank the engine for ten seconds and monitor PID reading.

Was there a pressure drop greater than 34 kpa (20 psi)? The Electronic Engine Control System is not the cause of the no start. REMOVE the fuel pressure gauge. RECONNECT the IFS switch. REFER to Section 3A, Symptom REMOVE fuel pressure gauge. RESTORE vehicle. GO to HA47. Charts for further diagnosis. HA47 CHECK VREF VOLTAGE AT NATURAL GAS VEHICLE MODULE Disconnect Natural Gas Vehicle (NG) module from harness. Install 60-pin breakout box. NG module connected. Measure the voltage between NG module Test Pin 26 and NG module Test Pin 46. Is the voltage reading between 4.0 and 6.0 volts? GO to HA56. VREF out of range. RESTORE vehicle. GO to HA48. HA48 WAS VREF GREATER THAN 6.0 VOLTS Was the VREF reading greater than 6.0 volts on the previous test step? VREF shorted to power. GO to HA54. VREF less than 4.0 volts. GO to HA49. HA49 CHECK BATTERY VOLTAGE Measure the voltage across the battery terminals. Is the voltage reading greater than 10.5 volts? GO to HA50. Key off. REFER to the Electrical/Battery and Charging System Group, Battery and Charging System Service/Charging System General Information Section in the Workshop Manual. HA50 CHECK VPWR AT NG MODULE Install 60-pin breakout box. NG module connected. Measure the voltage between VPWR circuit and PWR GND circuit. Is the voltage reading greater than 10.5 volts? GO to HA53. GO to HA51. HA51 CHECK VOLTAGE BETWEEN VPWR AT THE NG MODULE AND BATTERY GROUND Key on. Measure the voltage between VPWR circuit and battery ground. Is the voltage reading greater than 10.5 volts? GO to HA52. RESTORE vehicle. REPAIR open power circuit. HA52 CHECK FOR OPEN GROUND CIRCUIT IN HARNESS Breakout box installed. NGV module of the PWR GND circuit disconnected. Measure resistance between NG module Test Pins 40 and 60 and the battery negative post. Is the resistance less than 5.0 ohms? REPAIR ground circuit as necessary. RESTORE vehicle. GO to HA53. HA53 CHECK VREF VOLTAGE TO THE FUEL TANK PRESSURE SENSOR Locate fuel tank pressure sensor at the rear of the vehicle and disconnect (On the Crown Victoria, the fuel tank pressure sensor is located under the vent box cover of the upper tank assembly). Measure voltage between the VREF circuit and SIG RTN circuit at the fuel tank pressure sensor harness connector (refer to schematic at the beginning of this Pinpoint Test for pin

location). Is the voltage reading between 4.0 and 6.0 volts? FOLLOW Workshop Manual instructions. REPLACE Fuel Tank Pressure sensor. GO to HA55. HA54 CHECK VREF CIRCUIT FOR SHORT TO POWER IN HARNESS Fuel tank pressure sensor disconnected. Install 60-pin breakout box to NG module harness connector. NG module disconnected. Key on. Measure voltage between the VREF circuit and PWR GND circuit. Is the voltage reading less than 1.0 volt? RESTORE vehicle. REPLACE NG module. RESTORE vehicle. REPAIR short to power. HA55 CHECK VREF CIRCUIT FOR SHORTED TO PWR GND NG module disconnected. Measure resistance between VREF circuit and the SIG RTN, PWR GND and CASE GND. Is the resistance greater than 10,000 ohms? RESTORE vehicle. REPLACE NG module. RESTORE vehicle. REPAIR short to ground. HA56 CHECK FUEL INJECTOR(S) AND HARNESS RESISTANCE FROM THE NATURAL GAS (NG) MODULE TO THE FUEL INJECTOR(S) Disconnect NG module. Measure resistance between suspect fuel injector NG module Test Pin(s) and NG module Test Pins 37/57 (use chart for injector pin location). Cylinder Number Test Pin Cylinder Number Test Pin 1 58 5 33 2 59 6 42 3 39 7 53 4 35 8 54 Is the resistance between 3.0 and 6.0 ohms? Fuel injector(s) and harness resistance is OK from the NG module harness connector to the fuel injector(s). For Start and DTCs: GO to HA59. GO to HA57. HA57 CHECK FUEL INJECTOR(S) HARNESS RESISTANCE BETWEEN NG MODULE AND FUEL INJECTOR Measure resistance between the NG module harness connector Test Pins at the 60-Pin breakout box and the fuel injector(s) harness connector(s) at the fuel injector(s). Measure the resistance between the NG module harness connector Test Pins 37/57 at the breakout box and the fuel injector harness connector(s) (use chart for fuel injector pin location). Cylinder Number Test Pin Cylinder Number Test Pin 1 58 5 33 2 59 6 42 3 39 7 53 4 35 8 54 Is each resistance less than 5.0 ohms? GO to HA58. REPAIR open harness circuit. RESTORE vehicle. RERUN Quick Test. HA58 CHECK FUEL INJECTOR HARNESS CIRCUIT FOR SHORTS TO POWER AND GROUND Disconnect Scan Tool from DLC. Disconnect fuel injector(s) harness connector. Measure resistance between the fuel injector NG module Test Pin(s) and NG module Test Pins 37/57 and 40 or 60. Measure resistance between the fuel injector NG module Test Pin(s) and NG module Test Pin (20). Cylinder Number Test Pin Cylinder Number Test Pin

1 58 5 33 2 59 6 42 3 39 7 53 4 35 8 54 Is each resistance greater than 10,000 ohms? For DTCs P0172 and P0175, GO to HA61. REPLACE only damaged fuel injector(s). RESTORE vehicle. RERUN Quick Test. REPAIR short circuit. RESTORE vehicle. RERUN Quick Test. HA59 CHECK FUEL INJECTOR DRIVER SIGNAL AT 60-PIN BREAKOUT box This test requires a standard 12 volt test lamp. Connect NG module to breakout box. te: A properly operating system will show a dim glow at idle on the test lamp. Connect test lamp between NG module Test Pin 37 or 57 and fuel injector NG module Test Pin(s) 58, 59, 39, 35, 33, 42, 53 and 54 and crank or start the engine. Does the test lamp have a dim glow while cranking or running the engine? PCM and NG circuits are OK. RESTORE vehicle. For no starts, RETURN to Section 3A, Symptom Charts. All others: light/continuous bright light, GO to HA60. GO to HA63. HA60 CHECK PCM FUEL INJECTOR HARNESS CIRCUIT RESISTANCE Both 104 and 60-pin breakout boxes installed, PCM and NG module disconnected. Measure resistance between VPWR circuit PCM Test Pin 71 at the 104-pin breakout box and VPWR circuit NG Test Pin 37 or 57 at the 60-pin breakout box. Measure resistance between the Fuel Injector Test Pin(s) at the breakout boxes (refer to chart for test pin location). Cylinder Number PCM Output to 60-Pin NG Input PCM Test Pin NG Test Pin 1 75 3 2 101 4 3 74 5 4 100 23 5 73 24 6 99 25 7 72 43 8 98 44 Is each resistance less than 5.0 ohms? GO to HA61. REPAIR open harness circuit. RESTORE vehicle. RERUN Quick Test. HA61 CHECK PCM FUEL INJECTOR CIRCUIT FOR SHORT TO POWER AND GROUND IN HARNESS Measure resistance between the Fuel Injector PCM circuit Test Pin(s) and Test Pins 71 and PCM Test Pins 24, 25, 76 and 103 at the 104-pin breakout box (refer to chart in HA60 ). Measure the resistance between the Fuel Injector NG circuit Test Pin(s) 3, 4, 5, 23, 24, 25, 43 and 44 and NG Test Pin(s) 37, 57, 40, 60 at the 60-pin breakout box (refer to chart in HA60 ). Measure resistance between the Fuel Injector NG circuit Test Pin(s) 3, 4, 5, 23, 24, 25, 43 and 44 and Test Pin 20 at the 60-pin breakout box. Is each resistance greater than 10,000 ohms? For DTCs P0172 and P0175: GO to HA63. REMOVE 60-pin breakout box. RECONNECT NG module. GO to HA62. REPAIR short circuit. RESTORE vehicle. RERUN Quick Test. HA62 CHECK FUEL INJECTOR DRIVER SIGNAL FROM PCM This test requires a standard 12 volt test lamp. 104-pin breakout box installed, PCM connected to breakout box. te: A properly operating system will show a dim glow or flicker at idle on the test lamp.

Connect test lamp between VPWR circuit PCM Test Pin 71 and Fuel Injector circuit PCM Test Pin(s) 75, 101, 74, 100, 73, 99, 72 and 98 while cranking or starting the engine. Does the test lamp have a dim glow while cranking or starting the engine? For no starts: REPLACE NG module. RESTORE vehicle. RERUN Quick Test. For DTCs: light/continuous bright light. REPLACE PCM. RESTORE vehicle. RERUN Quick Test. RESTORE vehicle. GO to HA63. HA63 FLOW TEST FUEL INJECTOR(S) Use the Rotunda Natural Gas (NG) Injector Tester found in the Special NG Tool Kit 1-00114 or equivalent to flow test NG fuel injectors according to the instructions for the injector tester or test steps located in Pinpoint Test Step HB15. Is the leakage and flow within specification? DTCs P0171, P0172, P0174 and P0175: The fault that produced the DTC is an intermittent. GO to Pinpoint Test Step Z1 with the following data: SF1, SF2, LFT1, LFT2 PIDs and list of Possible causes. DTCs P10 and P1150: GO to HA65. REPLACE fuel injector. RERUN Quick Test. All others: GO to HA64. HA64 CHECK CYLINDER COMPRESSION te: Use the misfire DTC(s) displayed on prior DTC retrieval to determine which cylinder's compression to check. Check cylinder compression. Refer to Powertrain/Engine Group Base Engine/Engine Service Section of the Workshop Manual. Are cylinder compression readings within specification? For DTCs P11, P10, P1151 and P1150: GO to HA65. For DTCs P12 and P1152: REPAIR as necessary. RESTORE vehicle. RERUN Quick Test. GO to HA70. HA65 CHECK HO2S INTEGRITY Diagnostic Trouble Codes (DTCs) P11 and P1151 and/or P10 and P1150 indicate HO2S always lean, slow to switch, lack of switching or fuel at fuel trim. Moisture inside the HO2S harness connector resulting in a short to ground. HO2S coated with contaminants. HO2S circuit open. HO2S circuit shorted to ground. Inspect HO2S harness for chafing, burned out wires or other damage and service. Inspect HO2S and connector for indications of submersions in water, oil and coolant. Repair as necessary. Run engine at 2000 rpm for two minutes. Perform Key On Engine Running (KOER) Self-Test. Are DTCs P11 and/or P1151 present? GO to HA66. HO2S system is OK. Fuel delivery system is OK. Faults could have been repaired during inspection. Testing is complete at this time. HA66 CHECK HO2S's ABILITY TO GENERATE A VOLTAGE GREATER THAN 0.5 VOLT Any vacuum or air leaks can cause DTCs P11, P1151, P10 and P1150. Leaking vacuum actuators. Engine sealing (intake and IAC). EGR system (valve).

PCV system (hose and valve). Unmetered air leaks between throttle body and mass air flow (MAF) sensor assembly. Silicone contaminated HO2S. Disconnect the suspect HO2S from vehicle harness. Connect digital multimeter to the HO2S Signal circuit and HO2S SIG RTN circuit or HO2S GND circuit at the HO2S sensor connector. Run engine at 2000 rpm for two minutes. Rerun KOER Self-Test and monitor HO2S voltage. Does voltage reading indicate greater than 0.5 volt during or at the end of Self-Test? GO to HA67. REPLACE HO2S. RERUN Quick Test. HA67 CHECK HO2S SIGNAL AND HO2S GROUND CIRCUITS FOR OPEN IN HARNESS Breakout box installed, PCM disconnected. Disconnect suspect HO2S from harness. Inspect both ends of connector for damaged or pushed out pins, moisture, corrosion and loose pins. Repair as necessary. Measure the resistance between HO2S Signal circuit Test Pin and the HO2S vehicle harness connector. Use the Pin assignment below and record the reading. Measure resistance between SIG RTN circuit test pin and HO2S SIG RTN vehicle harness connector. Record readings. HO2S-11 SIG = test pin 60 HO2S-21 SIG = test pin 87 HO2S SIG RTN = test pin 91 Is the resistance reading less than 5.0 ohms? GO to HA68. REPAIR open circuit. RESTORE vehicle. RERUN Quick Test. HA68 CHECK HO2S CIRCUIT FOR SHORT TO GROUND IN HARNESS Measure resistance between the HO2S Signal circuit PCM Test Pin and PCM Test Pins 24, 77 and 103. Is each resistance greater than 10,000 ohms? GO to HA69. REPAIR short circuit. RESTORE vehicle. RERUN Quick Test. HA69 CHECK HO2S FOR SHORT TO GROUND Measure resistance between PWR GND/SIG RTN circuit PCM Test Pin and HO2S Signal circuit PCM Test Pin: HO2S-11 SIG = test pin 60 HO2S-21 SIG = test pin 87 HO2S PWR GND = test pin 24 and 103 HO2S SIG RTN = test pin 91 Is resistance greater than 10,000 ohms? For DTCs P10 and P1150: GO to HA70. For DTCs P11C and P1151C: GO to HA75. For KOER DTCs P11 and P1151: RESTORE vehicle. REPLACE PCM. REPLACE HO2S. RESTORE vehicle. RERUN Quick Test. HA70 CHECK FOR DTCS P12 AND P1152 WITH P10 AND P1150 Activate Key On Engine Running (KOER) Self-Test. Are DTCs P12 or P1152 present? GO to HA71. The fault that produced the DTC is an intermittent. GO to Pinpoint Test Step Z1 with the following data: HO2S-11, 21 PIDs and list of Possible causes. HA71 CHECK HO2S SIGNAL FOR SHORT TO VPWR and VREF Diagnostic Trouble Codes (DTCs) P12 and P1152 and/or P10 and P1150 indicate HO2S always rich. Moisture inside the HO2S harness connector resulting in a short to power. HO2S circuit shorted to power.

DTC P10, P12=H02S-11 DTC P1150, P1152=HO2S-21 te: HO2S displayed as O2S on Scan Tool. Access the Parameter Identification (PID) for the DTC generated. Is the voltage greater than 1.0 volt and less than 4.0 volts? An over voltage condition exists in the HO2S circuit. GO to HA72. GO to HA74. HA72 CHECK HO2S CIRCUIT FOR SHORT TO VPWR AND VREF Disconnect Scan Tool from DLC. Suspect sensor disconnected. Disconnect PCM. Install breakout box, leave PCM disconnected. Use the following list to measure the resistance between the appropriate PCM circuit test pins at the breakout box: DTC P10, P12=HO2S-11 test pin 60 and PCM circuit test pins 71 and 93 DTC P1150, P1152=HO2S-21 test pin 87 and PCM circuit test pins 71 and 93. Is the resistance greater than 10,000 ohms? RESTORE vehicle. GO to HA73. REPAIR short to power. RESTORE vehicle. RERUN Quick Test. HA73 CHECK HO2S SIGNAL FOR SHORT TO HO2S HEATER CIRCUIT IN THE SENSOR Suspect HO2S sensor disconnected. te: HO2S displayed as O2S on Scan Tool. Access HO2S PID corresponding to DTCs received. Is the HO2S voltage less than 0.2 volt? REPLACE HO2S. RESTORE vehicle. RERUN Quick Test. REPLACE PCM. RESTORE vehicle. RERUN Quick Test. HA74 ATTEMPT TO GENERATE DTCS P11 AND P1151 HO2S disconnected. Jumper HO2S Signal at the HO2S harness vehicle connector to the battery negative post. Activate Key On Engine Running (KOER) Self-Test. Are DTCs P11 or P1151 present? REMOVE jumper. GO to HA75. REMOVE jumper. RECONNECT HO2S. DISCONNECT PCM. INSPECT both ends of connector for damaged or pushed out pins, moisture, corrosion, loose pins. REPAIR as necessary. If OK, REPLACE PCM. RESTORE vehicle. RERUN KOER Self-Test. HA75 HO2S SENSOR VOLTAGE CHECK Suspect HO2S disconnected. Connect digital multimeter to HO2S Signal circuit and HO2S SIG RTN circuit at the HO2S sensor connector. Disconnect vacuum hose from vacuum tree. Start engine and run at 2000 rpm. Does the voltage reading indicate less than 0.4 volt within 30 seconds? RESTORE vehicle. GO to HA76. REPLACE HO2S. RESTORE vehicle. RERUN Quick Test. HA76 MONITOR HO2S (PID) FOR PROPER SWITCHING Key on, engine running. Engine at operating temperature.

te: HO2S displayed as O2S on Scan Tool. Access HO2S PID for suspect HO2S using Scan Tool. Access HO2S PID while wiggling, bending, and shaking small sections of the Electronic Engine Control harness from the PCM to the HO2S. Did the HO2S voltage stay high (greater than 0.45 volt) or low (less than 0.45 volt)? ISOLATE cause of lack of HO2S switches and repair. COMPLETE PCM Reset to clear DTCs. RERUN Quick Test. GO to HA77. HA77 TEST DRIVE WHILE MONITORING HO2S PID FOR PROPER SWITCHING te: This test step requires an observer to monitor PID for proper operation. Scan Tool still attached. Access HO2S PID. While observer views PID, test drive vehicle under different road conditions in an attempt to simulate the original fault. Does HO2S appear to switch properly? UNABLE to duplicate fault. COMPLETE PCM Reset to clear DTCs. Testing complete at this time. REPLACE HO2S. COMPLETE PCM Reset to clear DTCs. RERUN Quick Test. HA80 DTCS P17, P18, P1157 AND/OR P1158 LACK OF DOWNSTREAM HO2S SWITCHING Key On, Engine Running (KOER) Diagnostic Trouble Codes (DTCs) P17, P18, P1157 and P1158 can only be retrieved during KOER Self-Test when the fuel control is ramped rich and lean and monitored for a voltage change on the downstream HO2S. Wiring Concerns Pinched, shorted, and corroded wiring and pins Other Concerns Exhaust leaks Inoperative PCM Contaminated or damaged sensor Are any of the above concerns present? REPAIR as necessary. RERUN Quick Test. GO to HA81. HA81 CHECK EXHAUST SYSTEM FOR LEAKS te: Any exhaust leaks between the engine and the end of the catalyst can cause these DTCs. Place vehicle on a hoist, transmission in PARK, emergency brake applied, raise vehicle. Inspect the following: Exhaust flanges for leaks. HO2S torque. Check for punctures and cracks in catalyst and pipes leading to them. Are there any exhaust leaks? REPLACE or REPAIR as required. RERUN Quick Test. GO to HA82. HA82 CHECK HO2S CIRCUIT PCM connected to vehicle harness. Suspect HO2S connected to vehicle harness. te: HO2S displayed as O2S on Scan Tool. Access the correct HO2S PID. DTC HO2S PINS P17, P18 HO2S-12 35 and 71 P1157, P1158 HO2S-22 61 and 71 Is the voltage greater than 1.60 volts? REPLACE HO2S. RESTORE vehicle. RERUN Quick Test. GO to HA83.

HA83 CHECK HO2S HARNESS CIRCUIT FOR SHORT TO VPWR AND PWR GND Disconnect Scan Tool from DLC. Breakout box installed, PCM disconnected. HO2S disconnected. Measure resistance between HO2S SIG circuit PCM Test Pin and SIG RTN circuit PCM Test Pin. Measure resistance between HO2S SIG circuit PCM Test Pin and VPWR and VREF circuit PCM Test Pin. Measure resistance between HO2S Signal circuit PCM Test Pin and PWR GND circuit PCM Test Pin. HO2S-12 SIG = test pin 35 HO2S-22 SIG = test pin 61 HO2S SIG RTN = test pin 91 PWR GND = test pins 24 and 103 VPWR = test pin 71 VREF = test pin 90 Is resistance greater than 10,000 ohms? GO to HA84. REPAIR short in harness. RERUN Quick Test. HA84 CHECK HO2S SIGNAL AND HO2S GROUND CIRCUITS FOR OPEN IN HARNESS Disconnect suspect HO2S from harness. Measure the resistance between HO2S Signal circuit PCM Test Pin and HO2S harness connector. Record readings. Measure resistance between SIG RTN circuit PCM Test Pin and HO2S SIG RTN harness connector. Record readings. HO2S-12 SIG = Test Pin 35 HO2S-22 SIG = Test Pin 61 HO2S SIG RTN = Test Pin 91 Is the resistance reading less than 5.0 ohms? REPLACE PCM. RESTORE vehicle. RERUN Quick Test. REPAIR open circuit in harness. RESTORE vehicle. RERUN Quick Test. HA90 DTC P1127 KOER Key On, Engine Running (KOER) Diagnostic Trouble Code (DTC) P1127 indicates the HO2S heater(s) were not on during KOER self-test and testing of the HO2S did not occur. The HO2S heaters are turned on and off when certain temperatures are reached. The HO2S heaters are activated based on exhaust temperature modeling, which allows upstream heaters to be energized independently of the downstream heaters. Engine not operating long enough prior to performing KOER Self-Test. Exhaust system too cool. Access HTR11, 12, 21, 22 and monitor PIDs. Do all PIDs indicate ON? With engine still running, PERFORM KOER Self-Test. OPERATE engine until all PIDs indicate ON. PERFORM KOER Self-Test. HA100 DTC P1128 AND P1129 KOER Key On, Engine Running (KOER) Diagnostic Trouble Codes (DTCs) P1128 and P1129 indicate that during KOER testing, either the upstream or the downstream or both HO2S signals are swapped from bank to bank. P1128 refers to the upstream HO2S. P1129 refers to the downstream HO2S. Crossed HO2S harness connectors. Crossed wiring at HO2S harness connectors. Crossed HO2S wiring at PCM 104-pin harness connector. Visually inspect HO2S harness connector(s) for any crossed or stretched wires or wire harnesses not mounted properly. Are there any indications of crossed connectors or wires? REPAIR as necessary. RERUN Quick Test. GO to HA101. HA101 VERIFY PROPER HO2S SIGNAL PIN LOCATION PCM disconnected, breakout box installed.

Disconnect both of the suspect HO2S sensors from the harness connector. P1128 = HO2S 11/21 Upstream P1129 = HO2S 12/22 Downstream Measure resistance between the PCM circuit Test Pin(s) and the HO2S harness connectors. HO2S-11-Test Pin 60 HO2S-21-Test Pin 87 HO2S-12-Test Pin 35 HO2S-22-Test Pin 61 Is the resistance less than 5.0 ohms? HO2S SIG circuit is OK. RESTORE vehicle. RERUN Quick Test. CONNECT HO2S connector to proper HO2S or RELOCATE HO2S signal pins in the PCM 104-pin harness connector or HO2S harness connector. RESTORE vehicle. RERUN Quick Test.