GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2002 🢒 Grand Prix 🢒 Body and Accessories 🢒 Instrument Panel, Gages, and Console 🢒 Engine Coolant Temperature Gage Inaccurate or Inoperative

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step tests for a short to ground in the signal circuit.

    2.

  2. This step tests for an open, a high resistance, or a short to voltage in the signal circuit.

    3.

  3. DTCs will be set in the PCM when you perform this diagnostic table.

Step

Action

Value(s)

Yes

No

Schematic Reference: Instrument Cluster Schematics

1

Did you perform the IPC Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

2
  1. Install a scan tool.
  2. Turn the ignition ON, with the engine OFF.
  3. With the scan tool, observe the ECT parameter in the PCM Engine Data 1 data list.

Does the ECT parameter match the engine coolant temperature gage display?

--

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

Go to Step 3

3

  1. Turn the ignition OFF.
  2. Disconnect the ECT sensor.
  3. Turn the ignition ON, with the engine OFF.

Does the engine coolant temperature gage display at or below the specified value?

37°C (100°F)

Go to Step 4

Go to Step 6

4

  1. Turn the ignition OFF.
  2. Connect the J 33431-C Signal Generator and Instrument Panel Tester between the signal circuit of the ECT sensor (terminal C) and a good ground.

    3. Important: Verify the J 33431-C resistance setting with a DMM.

  3. Set the resistance on the J 33431-C to 44 ohms.
  4. Turn the ignition ON, with the engine OFF.

Does the engine coolant temperature gage display at or above the specified value?

138°C (280°F)

Go to Step 7

Go to Step 5

5

Test the signal circuit of the ECT sensor for an open, for a high resistance, or for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

6

Test the signal circuit of the ECT sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

7

Inspect for a high resistance or a poor connection at the case ground of the ECT sensor.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 8

8

Inspect for poor connections at the harness connector of the ECT sensor. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

9

Inspect for poor connections at the harness connector of the IPC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

10

Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement in Engine Controls (3.1L) or to Engine Coolant Temperature Sensor Replacement in Engine Controls (3.8L).

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the IPC. Refer to Instrument Cluster Replacement .

Did you complete the replacement?

--

Go to Step 12

--

12

  1. Use the scan tool in order to clear the PCM DTCs.
  2. Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2