Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection

Coolant Temperature Sensor/Switch (For Computer)

Coolant Temperature:

1. With the ignition switch in the OFF position, disconnect the coolant temperature sensor connector.

Injection Electronics (Motronic Control Unit). Wiring Diagram:

2. Turn the ignition switch to the run (ON) position, and make the following voltage measurements at the connector (female half).

^ Brown/red wire (terminal 1) and ground = approx. 5 volts.

^ If not check wire to terminal 45 of the DME control unit harness connector for an open or short to voltage or ground.

^ If wire is OK, the DME control unit is defective.

^ Brown/red (terminal 1) and brown/orange (terminal 2) = approx. 5 volts.

^ If not check wire to ground for an open.

^ If all voltages are correct continue with step 3.


3. With the ignition switch in the OFF position, clear the DME control unit memory by disconnecting the DME control unit harness connector. Reconnect the control unit harness connector.
4. Replace the coolant temperature sensor.
5. Start the engine and warm it up to normal operating temperature, varying the load conditions.

^ If the check engine light remains off, retain the new coolant temperature sensor. End of test.

^ If the "Check Engine" light illuminates repeat the "SELF-DIAGNOSTIC PROCEDURES". If a code 1223 reoccurs the DME control unit is defective.