Oxygen Sensor Signal Check
- Remove ECM from instrument panel without disconnecting coupler. (Connect coupler if disconnected.) Warm engine to normal operating temperature and let it idle.
- Connect voltmeter between terminal Nos. 10 (oxygen sensor ground) and 19 (ground). If voltmeter indicator deflects between 0 and .8 volts when engine speed varies from idle to 1500-2000 RPM, feedback system is operating properly.
- If voltmeter indicator remains at zero, check for the following: oxygen sensor lead wire disconnected, intake system leak, air/fuel ratio too lean, pulse air constantly sent to exhaust, voltmeter inner resistance too small, or faulty oxygen sensor.
- If voltmeter does not deflect from about .8 volts, check for the following: engine not warmed up (choke operating), defective thermal switch, defective WOT micro switch, or disconnected mixture control solenoid lead wire.
- Connect ohmmeter negative (-) lead to terminal No. 20 and positive (+) lead to body ground. If ohmmeter indicator deflects, feedback system is operating properly.
- Install ECM to instrument panel, making sure coupler is connected.