Cruise Control Inoperative

Fig. 32 Cruise control wiring circuit. 1984:

1. Diagnosis of inoperative cruise control system should begin by entering diagnostics and noting trouble codes. To diagnose trouble codes displayed, refer to ``Trouble Code Diagnosis'' and ``DEFI Trouble Code Tests.''
2. Perform switch tests as described under ``Diagnosis'' under ``Switch Tests.'' If any switch test trouble codes are displayed and do not pass, the malfunction causing the code to display must be repaired because these switches provide inputs to the ECM. Without these inputs, the cruise control system will not operate.
3. Start engine, then turn ignition off. Within 2 seconds, turn ignition back on.
4. Turn on cruise enable switch, then enter code .9.6, actuator cycling test. Check cruise control vacuum and power valves to determine if they cycle on and off.
5. If power valve does not cycle, disconnect power valve electrical connector and connect suitable test lamp between harness connector pins. If lamp lights intermittently, replace power valve solenoid. If lamp lights and remains on, check for short circuit or improper connections in circuit 402, Fig. 32. If circuit is satisfactory, ECM or ECM connector is at fault.
6. If test lamp does not light, check for open circuit in circuits 151 and 402 or short circuit in circuit 402. If circuits are satisfactory, measure resistance across cruise power valve in both directions. If both readings are less than 20 ohms, replace valve and ECM. If either reading is greater than 20 ohms, check for a faulty ECM or ECM connector and repair or replace as necessary.
7. If power valve cycles, check if vacuum valve cycles. If vacuum valve cycles, check for binding cruise control mechanical linkage or damaged or bent vacuum hoses.
8. If vacuum valve does not cycle, disconnect vacuum valve electrical connector and connect suitable test lamp between harness connector pins.
9. If lamp lights, check circuit 403 for a short to ground. If circuit is satisfactory, fault is in ECM or ECM connector. Repair or replace as necessary.
10. If lamp does not light, check circuits 919 (86, 1985) and 403 for an open. If circuits are satisfactory, measure resistance across cruise control vacuum valve in both directions. If both readings are less than 20 ohms, replace valve and ECM. If either reading is greater than 20 ohms, check for a faulty ECM or ECM connector and repair or replace as necessary.
11. If lamp flashes in three second intervals, replace vacuum valve solenoid.