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Diagnosis & Testing: Notes

  1. Check Fuses Check ENGINE and STOP fuses located in interior fuse panel. If fuses are okay, go to step 4). If fuse is blown, go to next step.
  2. Replace blown fuse. If fuse does not blow again, go to step 4). If fuse repeatedly blows, go to next step.
  3. Check For Shorts Turn ignition off. Unplug 6-pin and 10-pin connectors from interior fuse panel. Unplug connectors from Brake On/Off (BOO) switch and speed control module, located behind left side of instrument panel. Check Yellow/Red and Black/White wires at fuse panel connector for short to ground. If no short exists, go to next step. Repair wiring as necessary. See WIRING DIAGRAMS  .
  4. Check Switch Unplug speed control switch connector. Measure resistance between Blue and Black/White wire terminals of switch while pressing buttons as specified in SWITCH RESISTANCE SPECIFICATIONS table. Press only one button at a time. If resistances are as specified, go to next step. If any measurement is not as specified, replace switch assembly.
    SWITCH RESISTANCE SPECIFICATIONS

    Button Ohms
    ON Greater Than 10,000
    OFF Less Than 5
    SET/ACCEL Approximately 680
    COAST Approximately 120
    RESUME Approximately 2200
  5. Check Disable Circuit Turn ignition off. Press brake pedal. Measure voltage at White/Green wire (A/T) or Blue/Orange wire (M/T) at 6-pin connector. If voltage is greater than 10 volts with the brake pedal depressed and less than one volt with pedal released, go to next step. If voltage is not as described, go to CRUISE DOES NOT DISENGAGE WHEN BRAKES ARE APPLIED.
  6. Check VSS Voltage Raise and support vehicle with drive wheels off the ground. Start engine and engage transmission. Measure AC voltage between Orange/Black wire and Blue/White wire at speed control amplifier connector. Compare voltage measurements with VSS VOLTAGE table. If voltage is not as specified, go to next step. If voltage is as specified, go to step 8).
    VSS VOLTAGE

    Speed MPH AC Volts
    5 1.40
    15 2.80
    25 3.85
    35 4.55
    45 5.00
    55 5.40
  7. Check VSS Circuit Turn ignition off. Disconnect speed control amplifier connectors. Disconnect VSS connector. Measure resistance of Blue/White wire between VSS and amplifier connector. Also check Blue/White wire for short to ground. Measure resistance between Orange/Black wire at amplifier connector and Brown/Light Green wire at VSS harness connector. Also check circuit for short to ground. If either circuit is open or shorted to ground, repair circuit as necessary. If both circuits are okay, replace VSS.
  8. Check ON Circuit Disconnect 6-pin connector from amplifier. Turn ignition on. While holding down cruise control ON button, measure voltage of Yellow/Blue wire at amplifier 6-pin connector. If voltage is less than 10 volts, go to next step. If voltage is greater than 10 volts, go to step 11).
    WARNING: Disable air bag system before working around steering column or removing any air bag system component. See appropriate AIR BAG RESTRAINT SYSTEM article.
  9. Check Power To Clockspring Turn ignition off. Disconnect air bag clockspring 4-pin connector. Turn ignition on. Measure voltage of Black/White wire at 4-pin clockspring connector (harness side). If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair open Black/White wire.
  10. Check Switch Circuit Turn ignition off. Disconnect speed control amplifier connectors. Disconnect clockspring connector. Measure resistance of Yellow/Blue wire between clockspring connector and amplifier connector. Also check Yellow/Blue wire for short to ground. If circuit is open or shorted to ground repair circuit as necessary. If circuit is okay, replace clockspring assembly.
  11. Check Power To Amplifier Disconnect 6-pin connector from amplifier. Turn ignition on. Measure voltage of Blue/Black wire at amplifier 6-pin connector. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair Blue/Black wire.
  12. Check Amplifier Ground Turn ignition off. Disconnect 6-pin connector from amplifier. Measure resistance between Black wire at amplifier 6-pin connector and ground. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open Black wire.
  13. Check Amplifier-To-Servo Circuits Turn ignition off. Disconnect 8-pin harness connector from amplifier. Disconnect harness connector from servo. Measure resistance of each wire (6) between amplifier and servo harness connectors. Check each circuit for continuity to ground. If resistance measurements indicate any wire is open or shorted to ground, repair as necessary. If all 6 circuits between amplifier and servo are okay, go to next step.
  14. Check Servo Resistance Reconnect servo harness connector. At amplifier connector, measure resistance between each pair of wires specified in SERVO RESISTANCE SPECIFICATIONS table. If resistances are as specified, go to next step. If any measurement is not as specified, replace servo.
    SERVO RESISTANCE SPECIFICATIONS

    Wire Pair Ohms
    GRN/WHT - GRN 20,000-30,000
    GRN/ORG - GRN/WHT 40,000-60,000
    GRN/ORG - GRN 20,000-30,000
    BLU - GRN/BLK 40-70
    BLU - BLU/RED 150-210
    GRN/BLK - BLU/RED 110-140
    CAUTION: In the following step, DO NOT connect Blue wire to ground for longer than one second.
  15. Servo Functional Test Using a fused jumper, connect battery voltage to Green/Black wire at speed control amplifier connector. Connect Blue/Red wire to ground. Start engine. Momentarily connect jumper wire between Blue wire at speed control module connector and ground. Remove jumper wire. If servo arm pulled in when jumper was connected, replace amplifier. If servo arm did not pull in, replace servo.
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