Temperature Gauge: Testing and Inspection

Temperature Gauge Always Indicates Full Scale Hot Or Full Scale Cold, Other Gauges Are OK

Diagnostic Aids
For full scale readings, the gauge may be indicating the correct coolant temperature. Problems not covered by this diagnostic table include the following:
- Low coolant level.
- Improper coolant mixture.
- Coolant leaks.
- Faulty coolant pump.
- Faulty thermostat.
- Gasket failure.
- Lack of lubrication.
- Lack of cooling fan operation.
This table covers problems with the gauge circuit, the gauge, and the sending unit, but not problems which cause actual overheating or underheating.

Step 1 - 7:

Step 8 - 10:

Test Description
The numbers below refer to steps on the diagnostic table.
2. The coolant temperature sensor (CTS) for the electronic control module (ECM) and the temperature gauge sending unit are close together on the engine block. Refer to the schematic to determine the correct wire color to verity that you are testing at the correct component.
3. The CTS for the ECM and the temperature gauge sending unit are close together on the engine block. Refer to the schematic to determine the correct wire color to verify that you are testing at the correct component.