Diagnostic Aids
For full scale readings, the gage may be indicating the correct coolant temperature. Conditions 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 conditions with the gage circuit, the gage, and the sending unit, but not conditions which cause actual overheating or underheating.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The engine coolant temperature (ECT) sensor for the engine control module (ECM) and the temperature gage 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.
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The ECT sensor for the ECM and the temperature gage 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.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 |
Does the temperature gage always read at the high end of the scale? | -- | Go to Step 2 | Go to Step 7 |
Disconnect the coolant temperature sending unit electrical connector. Does the temperature gage indicator point to the low end of the scale? | -- | Go to Step 3 | Go to Step 4 | |
Replace the coolant temperature sending unit. Did you complete the repair? | -- | System OK | -- | |
4 |
Does the temperature indicator now point to the low end of the scale? | -- | Go to Step 5 | Go to Step 6 |
5 | Repair the short to ground in the WH/BK or WH wire between the instrument cluster connector and the coolant temperature sending unit. Did you complete the repair? | -- | System OK | -- |
6 | Replace the temperature gage. Did you complete the repair? | -- | System OK | -- |
7 |
Does the voltage measure within the specified value? | 11-14 V | Go to Step 10 | Go to Step 8 |
8 | Use an ohmmeter to measure for an open circuit between the coolant temperature sending unit and the temperature gage. Is the circuit open? | -- | Go to Step 9 | Go to Step 10 |
9 | Repair the open circuit between the temperature sending unit and temperature gage. Did you complete the repair? | -- | System OK | -- |
10 |
Does the temperature gage move to the high end of the scale? | -- | Go to Step 3 | Go to Step 6 |
