Engine Coolant Temperature Sensor Test

Note:
The best way to resolve a Code 45 or driveability incident is to carefully go through ALL the steps contained within this bulletin.

A COOLER TEMPERATURE READING (HIGHER RESISTANCE) THAN THE ACTUAL TEMPERATURE WILL CAUSE A RICH MIXTURE

1. Compare the CONSULT readout to the actual engine temperature. Access this the same as for the ALPHA or MAFS reading, (touch start-> engine-> data monitor-> main signals-> [or ECM input signals] start-> now watch COOLANT TEMP/S). The coolant temperature should be comparable to like vehicles under the same conditions. NOTE: CONSULT will only indicate an incident coolant temperature sensor if the circuit is open or shorted, it cannot detect an inaccurate temperature sensor or excessive resistance in the coolant temperature sensor circuit.

2. Remove the connector at the coolant temperature sensor and check for any corrosion. This may require a mirror to carefully inspect the connector on the temperature sensor depending on the vehicle type. Clean or replace as necessary.

3. Test the coolant temperature sensor with a OHM meter:

1. Disconnect the engine coolant temperature sensor harness connector.





2. Check the resistance as shown in the figure.