GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Allow the engine to cool to room temperature.

With the ignition ON, does the temperature gage always read at the high end of the scale?

--

Go to Step 7

Go to Step 2

2

Disconnect the engine control module (ECM) electrical connector.

Does the temperature gage indicator drop to the low end of the scale?

--

Go to Diagnostic System Check - Vehicle

Go to Step 3

3

Inspect for a short to ground between the ECM and the temperature gage.

Is there a short to ground?

--

Go to Step 4

Go to Step 5

4

Repair the short to ground.

Is the repair complete?

--

System OK

--

5

Replace the temperature gage.

Is the repair complete?

--

System OK

--

6

  1. Disconnect the ECM.
  2. Turn the ignition ON.
  3. Measure the voltage at the ECM.

Does the voltage measure within the specified range?

11-14 V

Go to Step 9

Go to Step 7

7

Inspect for an open circuit between the ECM and the temperature gage.

Is there an open circuit?

--

Go to Step 8

Go to Step 5

8

Repair the open circuit between the ECM and the temperature gage.

Is the repair complete?

--

System OK

--

9

  1. Disconnect the ECM.
  2. Connect a jumper wire between the ECM connector and ground.
  3. Turn the ignition ON.

Does the temperature gage move to the high end of the scale?

--

Go to Diagnostic System Check - Vehicle

Go to Step 5