Fault Tracing
Fault tracing, cruise controlRoad test
Road test vehicle to verify a cruise control system malfunction. If the road test indicates an inoperative system, check the following:
Check speedometer operation.
Check fuse #1.
Check all electrical connectors in the system.
Check brake light operation.
Check clutch adjustment.
Check for vacuum at vacuum reservoir with engine running.
Check vacuum switches by disconnecting the vacuum line marked servo at the vent valve, and blowing into it. The line should be air tight.
The most accurate method of fault tracing this cruise control system requires the use of special tool # 9990943-4. The test unit was developed to check the functions of all components including the control unit.
Connecting Cruise Control Tester
Remove left-hand under-dash panel. Disconnect cruise control harness from control unit. Connect tester lead to the control unit. Connect the cruise control wiring harness to tester unit.
Tester switch must be in position 1.
Turn ignition key to position II. DO NOT start engine.
TEST #6 Speed Signal
Raise left rear wheel off ground. Rotate wheel slowly while watching SPEED light on tester. Light should blink on and off with low light intensity.
NOTE: On vehicles equipped with limited-slip differential, both rear wheels must be raised off ground and transmission placed in neutral.
TEST #7
CAUTION: Turn Cruise Control OFF,
Start engine to build up vacuum
THEN, TURN ENGINE OFF
Turn ignition key to position II
Turn cruise control on.
Depress VAC and VENT buttons on tester simultaneously. Throttle pedal should be pulled down to floor. If not, check the following:
Check vacuum supply.
Verify that tests 1-6 are correct.
Replace control unit.
Release the VAC button on tester and keep the VENT button depressed for a minimum 15 seconds. The throttle pedal should remain steady. If not, the system has a vacuum leak.
TEST RESULTS
If tester lamps do not light in correct sequence, check the following:
Ignition Lamp:
Main power supply to cruise system.
Check fuse #12 and wiring.
Resume and Set Lamps:
Check yellow and green wires between control unit and switch. If OK, replace switch.
Brake/Clutch Lamp:
Check adjustment of switches on pedals.
Check wiring. Check brake light operation.
Speed Lamp:
Verify proper speedometer operation. Check for proper connection of orange wire to rear of instrument cluster.
Vac and Vent Lamp:
Check the three wires going to the servo valve under the hood.
yellow/red wire
yellow/brown wire
white/red wire
Check cruise control switch
Disconnect the connector at the cruise control switch.
Connect a jumper wire from 12V current source (for instance, the fuse box) to red wire terminal in connector.
Connect a test light across ground and the three wires, in order.
Correct test light indication is shown in table below. Replace the cruise control switch in case of incorrect indication.
