GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Does the speedometer work?

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Go to Step 2

Go to Instrument Cluster Indicators and Gauges Inoperative

2

  1. Disconnect the engine coolant temperature (ECT) sensor connector.
  2. Connect the instrument panel tester tool J 33431-C between the engine coolant temperature (ECT) sensor harness connector terminal C and ground.
  3. Set the tester to 44 ohms.
  4. Turn the ignition switch to the RUN position.

Does the engine coolant temperature gauge read high [approximately 125° C (260° F)]?

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Go to Step 3

Go to Step 8

3

Set the tester to 1365 ohms.

Does the engine coolant temperature gauge read low [approximately 37° C (100° F)]?

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Go to Step 4

Go to Step 5

4

  1. Check the engine coolant temperature (ECT) sensor connector for a poor connection.
  2. If OK, replace the engine coolant temperature (ECT) sensor. Refer to Engine Coolant Temperature Sensor Replacement in Engine Controls.

Has the repair been made and the system rechecked?

--

System OK

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5

Check for a poor connection or short to voltage in circuit 135.

Is there a poor connection or short to voltage in circuit 135?

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Go to Step 6

Go to Step 7

6

Repair poor connection or short to voltage in circuit 135.

Has the repair been made and the system rechecked?

--

System OK

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7

Replace the instrument cluster. Refer to Instrument Cluster Replacement .

Has the repair been made and the system rechecked?

--

System OK

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8

Check for a poor connection, open or short to ground in circuit 135.

Is there a poor connection, open or short to ground in circuit 135?

--

Go to Step 9

Go to Step 7

9

Repair the poor connection, open or short to ground in circuit 135.

Has the repair been made and the system rechecked?

--

System OK

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