Coolant Temperature Sensor / Switch HVAC: Testing and Inspection
ECT Sensor Circuit Troubleshooting1. Check the malfunction indicator lamp (MIL).
Does the malfunction indicator lamp come on?
YES - Refer to the Fuel and Emissions section.
NO - Go to step 2.
2. Turn the ignition switch OFF.
3. Disconnect the ECT sensor 2P connector.
4. Disconnect climate control unit connector B (30P).
5. Turn the ignition switch ON (II).
6. Measure the voltage between the No. 22 terminal of climate control unit connector B (30P) and body ground.
Is there about 5 V?
YES - Check for loose wires or poor connections at climate control unit connector B (30P) and at the ECT sensor 2P connector. If the connections are good, substitute a known-good climate control unit, and recheck. If the symptom/indication goes away, replace the original climate control unit.
NO - Repair open in the wire between the climate control unit and the ECT sensor.