GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you perform the Instrument Cluster Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

2

Verify that the engine coolant temperature gauge is inaccurate or inoperative.

Does the engine coolant temperature gauge operate normally?

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Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

Important: There is a flat band in the gauge where the engine temperature is between 87.8-104.4°C (190-220°F) and the gauge remains at 93°C (200°F).

  1. Turn the ignition switch to the ON position.
  2. Ensure that the engine is running.
  3. Allow the engine to idle to normal operating temperature.
  4. Install the scan tool.
  5. Select the displayed coolant temperature display on the scan tool.
  6. Compare the displayed coolant temperature data on the scan tool to the temperature gauge reading on the cluster.

Are the temperatures approximately equal (or within 25°)?

87°C

(190°F)

Go to Step 4

Go to Step 7

4

Read the monitored coolant temperature from the scan tool.

Is the monitored coolant temperature reading within the specified range?

38-127°C

(100-260°F)

Go to Step 5

Go to Step 6

5

Compare the monitored coolant temperature with the displayed coolant temperature.

Are the temperatures approximately equal or within 11°C (25°F)?

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Go to Step 6

Go to Step 7

6

Important: There is a flat band in the gauge where the engine temperature is between 87.8-104.4°C (190-220°F) and the gauge remains at 93°C (200°F).

    • If the monitored coolant temperature is less than 38°C (100°F), the gauge should be at or near the lowest reading.
    • If the monitored coolant temperature is greater than 127°C (260°F), the gauge should be at or near the maximum reading.

Is the gauge reading correct?

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Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 7

7

Replace the instrument cluster. Refer to Instrument Cluster Replacement .

Did you complete the replacement?

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Go to Step 8

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8

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 3