Symptom Related Diagnostic Procedures

If cruise control is inoperative, enter ECM ``Input'' tests and perform the following, referring to ECM replacement check, if necessary, under SYSTEM DIAGNOSTIC CHARTS. For connector pin locations, refer to SCHEMATIC DIAGRAMS/ELECTRONIC AND ELECTRICAL DIAGRAMS/ELECTRICAL CONNECTORS.
If cruise system does function, but indicator does not light, proceed to step 13.
1. With ignition switch in Run position, on 1989 models, select ECM input test EI79, on 1990-91 models, select ECM input test E182.
2. If ECM does not display LO with cruise control switch off, or does not display Hi with cruise control switch on, on 1989 models, select ECM input test E179, on 1990-91 models, select PCM input test E182. For intermittent codes proceed as follows:
a. The amber cruise on indicator can be used to monitor cruise dash switch status. Turn dash switch on and wiggle wiring and connectors. If switch or circuit from fuse to switch are open, amber light will blink out.
b. If cruise 3A fuse blows intermittently, turn switch on, wiggle wiring, connectors, cruise steering column switch. If circuit becomes grounded, the fuse will blow.
3. If ECM displays LO with cruise switch on and displays HI with cruise switch on, on 1989 models, select ECM input test EI71, on 1990-91 models, select input test E170, on all models, turn ignition switch to Run position and cruise switch on.
4. If ECM does not display LO with brake pedal depressed, or does not display HI with brake pedal released, on 1989 models, select ECM input test E171, on 1990-91 models, select PCM input test E170.
5. If ECM displays LO with brake pedal depressed and HI with brake pedal released, on 1989 models, select ECM input test EI81, on 1990-91 models, select ECM input test E184, on all models turn ignition switch to Run position and cruise control on.
6. If ECM does not display HI with Resume/Accelerate switch depressed, or does not display LO with resume/accelerate switch released, on 1989 models, select ECM input test E181, on 1990-91 models, select PCM input test E184. For intermittent codes proceed as follows:
a. Turn cruise dash switch to on and backprobe ECM B6 with a voltmeter to ground, B6 should show 12 volts with Resume/Accelerate depressed and 0 volts with Resume/Accelerate released. Cycle switch while observing the meter, wiggle wiring and connectors.
7. If ECM displays HI with resume/accelerate switch depressed and displays LO with resume accelerate switch released, on 1989 models, select ECM input test EI81, on 1990-91 models, select ECM input test E183, on all models, turn ignition switch to Run position and cruise switch on.
8. If ECM does not display HI with resume/accelerate switch depressed, or does not display LO with resume/accelerate switch released, on 1989 models, refer to ECM input test E180, on 1990-91 models, select PCM input test E183. For intermittent codes proceed as follows:
a. Turn cruise dash switch to on and backprobe ECM B4 with a voltmeter to ground. B4 should show 12 volts with resume/accelerate depressed and 0 volts with resume/accelerate released. Cycle switch while observing meter, wiggle wiring and connectors.
9. If ECM displays HI when resume/accelerate switch is depressed and displays LO when resume/accelerate switch is released, run engine for 2 minutes, then turn engine off and select ECM override test ES04.
10. Vary override from 0 to 99, then to 0 again.
11. If cruise control servo does not pull fully in and then release, check vacuum source and hoses for leaks, kinks or restrictions and check servo linkage for mechanical binding, then replace cruise control servo as necessary.
12. If cruise control servo pulls fully in and then releases, replace ECM.
13. If cruise On indicator does not light, but cruise system does function, proceed as follows:
a. Remove right switch assembly and connect test lamp between connector terminals B4 and BC1.
b. If lamp illuminates, on 1989-90 models replace, right switch assembly.
c. If lamp does not illuminate, check flex circuit 804, repairing as necessary.