GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

DEFINITION: A normal temperature gauge is considered to be when the needle is pointing to the middle of the gauge, in a vertical position.

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

1

Did you perform the Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check

2

  1. Ensure that the cooling system is full. Refer to Cooling System Draining and Filling .
  2. Allow the engine/radiator cap to cool.
  3. Start the engine with the A/C OFF.
  4. Inspect the engine cooling fans.

Is either cooling fan on?

--

Go to Step 4

Go to Step 3

3

  1. Diagnose and repair the cooling fan system. Refer to Electric Cooling Fan Diagnosis in Engine Controls.
  2. Verify the customer complaint.

Does the engine still fail to reach normal operating temperature?

--

Go to Step 4

System OK

4

Install the scan tool and compare the coolant temperature reading with the I/P gauge.

Does the scan tool coolant temperature reading coincide with a normal temperature gauge reading?

--

Go to Step 6

Go to Step 5

5

  1. Diagnose and repair the coolant gauge system. Refer to Engine Coolant Temperature Gage Inaccurate or Inoperative in Instrument Panel Gauges and Console.
  2. Verify the customer complaint.

Does the engine still fail to reach normal operating temperature?

--

Go to Step 6

System OK

6

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

Does the thermostat operate properly?

--

Go to Diagnostic System Check

Go to Step 7

7

  1. Replace the thermostat. Refer to Engine Coolant Thermostat Replacement .
  2. Verify the customer complaint.

Does the engine still fail to reach normal operating temperature?

--

Go to Step 8

System OK

8

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2