GM Service Manual Online
For 1990-2009 cars only

Diagnostic Aids

The engine may fail to reach normal operating temperature due to an intermittent operation of one of the following components:

    • The thermostat
    • The electric fan system
    • The mechanical fan system

For electrical inspection of the electrical fan system, refer to Testing for Intermittent Conditions and Poor Connections .

Step

Action

Yes

No

DEFINITION: Normal coolant temperature readings will be expected to vary from 88-104°C (190-220°F).

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Verify that the engine fails to reach normal operating temperature.

Is the engine failing to reach normal operating temperature?

Go to Step 3

Go to Diagnostic Aids

3

Inspect the surge tank for low coolant.

Is there a loss of coolant?

Go to Loss of Coolant

Go to Step 4

4

Inspect the thermostat for proper operation. Refer to Thermostat Diagnosis .

Does the thermostat operate properly?

Go to Step 6

Go to Step 5

5

Replace the thermostat. Refer to Engine Coolant Thermostat Replacement .

Did you complete the repair?

Go to Step 6

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6

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2