Troubleshooting

1. Test 10 or 15 mph speed sensor as outlined under ``Speed Sensor, Test'' procedure.
2. Test thermosensor as follows:
a. Ensure that engine is sufficiently cold by disconnecting hose No. 19 at charcoal canister. There must be no vacuum at idle.
b. Disconnect connector at control unit.
c. Check for resistance between blue/yellow and brown/black terminal on 1985-87 models. Resistance should be above 1k ohm.
d. Run engine until it reaches normal operating temperature, then check resistance again. Resistance should be approximately 200 ohms.
e. If resistance is not within specifications, replace thermosensor and repeat test.
f. If ohmmeter shows no continuity, check wires.
g. If wires are satisfactory, replace thermosensor and repeat test.
3. Turn ignition switch on and check for voltage at black/yellow wire at control unit connector. If there is no voltage, check wiring.
4. Ensure brown/black wire shows continuity between control unit and suitable ground.
5. If no faults are found in steps 1 through 5, replace control unit and repeat test.