Troubleshooting

PRELUDE

1. Turn ignition switch on and check for voltage at blue wire at control unit connector. If there is no voltage, check blue wire between ignition coil and control unit.
2. Test 10 or 15 mph speed sensor as outlined under ``Speed Sensor, Test'' procedure.
3. Test thermosensor as follows:
a. Ensure that engine is cold by disconnecting vacuum hose No. 19 at charcoal canister. There must be no vacuum at idle.
b. Disconnect connector at control unit.
c. Check resistance between blue/yellow and brown/black terminals. 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.
4. Turn ignition switch on and check for voltage at black/yellow wire at control unit connector. If there is no voltage, check wiring.
5. Check black or brown/black wire for continuity between control unit and suitable ground. There should be continuity.
6. Test intake air temperature switch as follows:
a. Disconnect intake air temperature switch electrical connector, then check continuity between terminals.
b. Continuity should not be present if air temperature is above 73 degrees F. Continuity should be present if air temperature is below 40 degrees F. Replace sensor as required.
7. Inspect vacuum switches for proper operation.
8. If no faults are found, replace control unit and repeat test.