Page 1 of 7 Service Manual: CRUISE CONTROL SYSTEMS DESCRIPTION 1998 Ford Econoline 6.8L Eng E350 NOTE: On 7.3L diesel, all speed control functions are controlled by the PCM. See TESTS W/CODES - DIESEL article in the ENGINE PERFORMANCE section for diagnostic procedures. Wiring diagram for 7.3L diesel engine speed control is included in this article. The cruise control system consists of control switches (ON, OFF, SET-ACCEL, COAST and RESUME), servo throttle servo/actuator assembly, deactivator switch and wiring. Vehicle speed signal comes from Powertrain Control Module (PCM). TROUBLE SHOOTING Before performing any testing, check the following for possible cause of system malfunction: Faulty fuses. Loose or corroded connections. Damaged wiring harness. Damaged switches. Damaged or binding actuator cable. Incorrect actuator cable adjustment. Verify horn and stoplights function properly. Repair as necessary. Inspect actuator and throttle linkage for smooth Unbind as necessary. If no problems are found, perform appropriate test based upon symptom. See SYSTEM TESTS. SYSTEM TESTING NOTE: Before performing any testing, perform trouble shooting. Repair as necessary. Check PCM for stored Diagnostic Trouble Codes (DTCs). See appropriate TESTS W/CODES article in the ENGINE PERFORMANCE section for diagnostic procedures.

Page 2 of 7 NOTE: On 7.3L diesel, speed control functions are controlled by the PCM. See TESTS W/CODES - DIESEL article in the ENGINE PERFORMANCE section for diagnostic procedures. SYSTEM TESTING > TEST A: SPEED CONTROL IS INOPERATIVE 1. Check For Voltage To Servo/Actuator - Turn ignition off. Disconnect speed control servo/actuator connector C146 (located near master cylinder). Turn ignition on. Using a voltmeter, check voltage between servo/actuator connector C146 terminals No. 7 and 10. See Fig 1. If voltage is 10 volts or less, go to next step. If voltage is more than 10 volts, go to step 4). 2. Check Fuse - Turn ignition off. Check instrument panel fuse block fuse No. 6 (10-amp). If fuse is okay, go to next step. If fuse is blown, replace fuse. If fuse fails again, repair short to ground in Purple/Orange wire. Retest system 3. Check Servo/Actuator Ground Circuit - Turn ignition off. Using an ohmmeter, check resistance between ground and speed control servo/actuator connector C146 terminal No. 10. See Fig 1. If resistance is less than 5 ohms, repair Purple/Orange wire between instrument panel fuse block and speed control servo/actuator. Retest system If resistance is 5 ohms or more, repair Pink/Orange wire between speed control servo/actuator and ground. Retest system 4. Check Stoplight Operation - Check stoplight operation while pressing and releasing brake pedal. If stoplights operate properly, go to next step. If stoplights do not operate properly, see appropriate EXTERIOR LIGHTS wiring diagram in SYSTEM WIRING DIAGRAMS article in the WIRING DIAGRAMS section to continue diagnosis. 5. Check Light/Green Wire - Turn ignition off. Disconnect speed control servo/actuator connector C146 (located near master cylinder). Using an ohmmeter, check resistance between speed control servo/actuator connector C146 terminals No. 4 and 10. See Fig 1. If resistance is less than 20 ohms, go to next step. If resistance is 20 ohms or more, repair Light Green wire. Retest system 6. Check Deactivator Switch Input To Speed Control Servo/Actuator - Ensure ignition is off. Using a voltmeter, check voltage between speed control servo/actuator connector C146 terminals No. 9 and 10. See Fig 1. If voltage is 10 volts or less, go to next step. If voltage is more than 10 volts, go to step 9). 7. Check Deactivator Switch - Ensure ignition is off. Disconnect deactivator switch connector C151 (located on bottom of brake master cylinder). Using an ohmmeter, check resistance between deactivator switch terminals (component side). If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, replace deactivator switch and bleed brake system. Retest system 8. Check For Voltage To Deactivator Switch - Ensure ignition is off. Using a voltmeter, check voltage between ground and deactivator switch connector C151 Light Green/Red wire terminal. If voltage is more than 10 volts, repair Red/Light Green wire between deactivator switch and speed control servo/actuator. Retest system If voltage

Page 3 of 7 is 10 volts or less, repair Light Green/Red wire between instrument panel fuse block and deactivator switch. Retest system 9. Check Light Blue/Black Wire For Short To Voltage - Ensure ignition is off. Using a voltmeter, check voltage between speed control servo/actuator connector C146 terminals No. 5 and 10. See Fig 1. If voltage is present, go to next step. If no voltage is present, go to step 12). 10. Check For Stuck Speed Control Switch - Disconnect speed control switch connector from steering wheel. Turn ignition on. Using a voltmeter, check voltage between speed control servo/actuator connector C146 terminals No. 5 and 10. See Fig 1. If any voltage is present, go to next step. If no voltage is present, replace speed control switch and retest system 11. Check Light Blue/Black Wire For Short To Voltage - Disconnect air bag sliding contact connector C223 (located on top of steering column, near clockspring assembly). Turn ignition on. Using a voltmeter, check voltage between speed control servo/actuator connector C146 terminals No. 5 and 10. See Fig 1. If any voltage is present, repair Light Blue/Black wire. Retest system If no voltage is present, replace air bag sliding contact and retest system 12. Check SET/ACCEL Switch Operation - Using an ohmmeter, check resistance between speed control servo/actuator connector C146 terminals No. 5 and 6 while pressing speed control SET/ACCEL switch. If resistance is not 640-720 ohms, go to next step. If resistance is 640-720 ohms, go to step 15). 13. Check Light Blue/Black Wire For Open - Ensure ignition is off. Disconnect air bag sliding contact connector C223 (located on top of steering column, near clockspring assembly). Using an ohmmeter, check resistance in Light Blue/Black wire between speed control servo/actuator connector C146 terminal No. 5 and air bag sliding contact connector C223. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Light Blue/Black wire. Retest system 14. Check Air Bag Sliding Contact - Remove driver side air bag. See AIR BAG RESTRAINT SYSTEM article. Using an ohmmeter, check resistance between air bag sliding contact 5-pin male connector C253 terminal No. 1 and air bag sliding contact 6-pin male connector C223 terminal No. 1. See Fig 2. If resistance is less than one ohm, replace speed control switch and retest system If resistance is one ohm or more, replace air bag sliding contact and retest system 15. Check Speed Signal - Raise and support vehicle with rear wheels clear of ground. Start engine and maintain vehicle speed at 30 MPH. Set voltmeter to check AC voltage. Check voltage between speed control servo/actuator connector C146 terminals No. 3 and 10. See Fig 1. If voltage is not 4-5 volts and frequency is not 56-78 Hz, go to next step. If voltage is 4-5 volts and frequency is 56-78 Hz, got step 18). 16. Check Gray/Black Wire For Open - Disconnect vehicle speed sensor connector C108 (located on left side of transmission). Using an ohmmeter, check resistance in Gray/Black wire between speed control servo/actuator connector C146 terminal No. 3 and vehicle speed sensor connector C108. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Gray/Black wire. Retest system

Page 4 of 7 17. Check Pink/Orange Wire For Open - Using an ohmmeter, check resistance between ground and vehicle speed sensor connector C108 Pink/Orange wire terminal. If resistance is less than 5 ohms, replace vehicle speed sensor and retest system If resistance is 5 ohms or more, repair open in Pink/Orange wire between vehicle speed sensor and ground. Retest system 18. Check Speed Control Servo/Actuator Cable - Ensure ignition is off. Disengage speed control servo/actuator cable from servo/actuator. Inspect cable by pulling end of cable and observing throttle movement. Replace cable if broken or binding and retest system If cable is okay, replace servo/actuator and retest system Fig 1: Identifying Servo/Actuator Connector C146 Terminals Courtesy of FORD MOTOR CO.

Page 5 of 7 Fig 2: Checking Air Bag Sliding Contact Courtesy of FORD MOTOR CO. SYSTEM TESTING > TEST B: SET SPEED FLUCTUATES 1. Check Speed Control Servo/Actuator Cable & Throttle Body Linkage Ensure ignition is off. Disengage speed control servo/actuator cable from servo/actuator. Inspect cable by pulling end of cable and observing throttle movement. If cable is okay, go to next step. Replace cable if broken or binding and retest system 2. Check Speedometer Operation - Drive vehicle and observe speedometer operation without using speed control. If speedometer needle fluctuates, see ANALOG INSTRUMENT PANEL article to continue diagnosis. If speedometer needle does not fluctuate, replace speed control servo/actuator and retest system

Page 6 of 7 SYSTEM TESTING > TEST C: SPEED CONTROL DOES NOT DISENGAGE WHEN BRAKES ARE APPLIED 1. Check Speed Control Servo/Actuator Cable & Throttle Body Linkage - Ensure ignition is off. Disengage speed control servo/actuator cable from servo/actuator. Inspect cable by pulling end of cable and observing throttle movement. If cable is okay, go to next step. Replace cable if broken or binding and retest system 2. Check Stoplight Operation - Check stoplight operation while pressing and releasing brake pedal. If stoplights operate properly, go to next step. If stoplights do not operate properly, see appropriate EXTERIOR LIGHTS wiring diagram in SYSTEM WIRING DIAGRAMS article in the WIRING DIAGRAMS section to continue diagnosis. 3. Check Brake Pedal Position (BPP) Switch Input - Ensure ignition is off. Disconnect speed control servo/actuator connector C146 (located near master cylinder). Press and hold brake pedal. Using a voltmeter, check voltage between speed control servo/actuator connector C146 terminals No. 4 and 10. See Figure. If voltage is more than 10 volts, replace speed control servo/a actuator and retest system If voltage is 10 volts or less, repair Light Green wire between speed control servo/actuator and BPP switch. Retest system SYSTEM TESTING > TEST D: COAST SWITCH IS INOPERATIVE > CHECK COAST SWITCH OPERATION cylinder). While pressing COAST switch and rotating steering wheel from stop to stop, check Figure. If resistance is 114-126 ohms, replace speed control servo/actuator and retest system If resistance is not 114-126 ohms, replace speed control switch and retest system SYSTEM TESTING > TEST E: SET/ACCEL SWITCH IS INOPERATIVE > CHECK SET/ACCEL SWITCH OPERATION cylinder). While pressing SET/ACCEL switch and rotating steering wheel from stop to stop, check Figure. If resistance is 646-714 ohms, replace speed control servo/actuator and retest system If resistance is not 646-714 ohms, replace speed control switch and retest system

Page 7 of 7 SYSTEM TESTING > TEST F: RESUME FUNCTION INOPERATIVE > CHECK RESUME SWITCH OPERATION cylinder). While pressing RESUME switch and rotating steering wheel from stop to stop, check Figure. If resistance is 2090-2310 ohms, replace speed control servo/actuator and retest system If resistance is not 2090-2310 ohms, replace speed control switch and retest system SYSTEM TESTING > TEST G: OFF SWITCH IS INOPERATIVE > CHECK OFF SWITCH OPERATION cylinder). While pressing OFF switch and rotating steering wheel from stop to stop, check Figure. If resistance is 5 ohms or less, replace speed control servo/actuator and retest system If resistance is more than 5 ohms, replace speed control switch and retest system