Cruise Control Isolation Test

Cruise control isolation test is designed to isolate the individual functional systems within the cruise control system. Before performing test procedures, perform self-diagnostics, record and diagnose any trouble codes. See ENTERING SELF-DIAGNOSTICS and DISPLAYING TROUBLE CODES in appropriate G - TEST W/CODES article in the ENGINE PERFORMANCE Section.

Inspect cruise control servo throttle cable, cruise brake switch and Viscous Converter Clutch (VCC) brake switch for proper adjustment. Inspect vacuum hoses for kinks, leaks or restrictions.

1. Slide cruise control switch to OFF position. PCM input EI82 display should read LO. If display does not read LO, check for short to voltage in circuits No. 86 (Brown wire) and No. 397 (Gray wire). Repair shorted wire(s) as necessary.
2. Slide cruise control switch to ON position. PCM input EI82 display should read HI. If display does not read HI, Check fuse D5. Replace fuse, if necessary. Check for open in circuits No. 250 (Brown wire) and No. 397 (Gray wire). Repair wire(s) as necessary. Check circuits No. 86 (Brown wire), No. 250 (Brown wire) and No. 397 (Gray wire) for short circuit to ground. Repair wire(s) as necessary
3. Leave cruise control switch on and select PCM input EI70. Depress brake pedal. PCM input EI70 display should read LO. If display does not read LO, check cruise brake switch adjustment. Adjust switch, if necessary. Check for short to voltage in circuit No. 86 (Brown wire). Repair short, if necessary.
4. Release brake pedal. PCM input EI70 display should read HI. If display does not read HI, check cruise brake switch for adjustment or defect. Replace or adjust switch, if necessary. Check for open in circuits No. 86 (Brown wire) and No. 397 (Gray wire). Repair wire(s) as necessary.
5. Leave cruise control switch on and select PCM input EI71. Depress brake pedal. PCM input EI71 display should read LO. If display does not read LO, see code P090 in PCM TROUBLE CODES table in appropriate G - TEST W/CODES article in ENGINE PERFORMANCE Section.
6. Release brake pedal. PCM input EI71 display should read HI. If display does not read HI, see code P090 in PCM TROUBLE CODES table.
7. Leave cruise control switch on and select PCM input EI84. Slide cruise control switch to RESUME/ACCEL position. PCM input EI84 display should read HI. If display does not read HI, check for open in RESUME/ACCEL switch. Replace switch, if defective. Check for open in circuit No. 87 (Gray/Black wire). Repair wire, if necessary.
8. Release cruise control switch. PCM input EI84 display should read LO. If display does not read LO, check for shorted RESUME/ACCEL switch. Replace switch, if defective.
9. Depress SET/COAST button. PCM input EI84 display should read LO. If display does not read LO, check circuit No. 84 (Dark Blue wire) and circuit No. 87 (Gray/Black wire) for short to voltage. If Dark Blue and Gray/Black wires are okay, replace multifunction lever.
10. Select PCM input EI83 and leave cruise control switch on. Depress SET/COAST button. PCM input EI83 display should read HI. If display does not read HI, check for open in cruise SET/COAST switch. Replace switch, if defective. Check for open in circuit No. 84 (Dark Blue wire). Repair wire, if necessary
11. Release SET/COAST button. PCM input EI83 display should read LO. If display does not read LO, check for short in SET/COAST switch. If defective, replace switch. Check for short to voltage in circuit No. 84 (Dark Blue wire). Repair wire, if necessary.
12. Slide cruise control switch to RESUME/ACCEL position. PCM input EI83 display should read LO. If display does not read LO, check circuit No. 84 (Dark Blue wire) and circuit No. 87 (Gray/Black wire) for short to voltage to each other. If Dark Blue and Gray/Black wires are okay, replace multifunction lever. If all results are normal, go to CRUISE CONTROL OUTPUT TEST.