For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Instrument Cluster Schematics
1 | Did you perform the Instrument Cluster 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 Sensor parameter in the PCM Engine Data 1 data list.

Does the ECT Sensor parameter match the engine coolant temperature (ECT) 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 gage sensor.
3. Turn the ignition ON, with the engine OFF.

Does the ECT 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 gage sensor and a good ground.

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 ECT 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 gage 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 gage sensor for a short to ground. 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
7 | Test the ground circuit or the case ground of the ECT gage sensor for an open or for a high resistance. 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 8
8 | Inspect for poor connections at the harness connector of the ECT gage 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 to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11
10 | Replace the ECT gage sensor. Refer to Engine Coolant Temperature Sensor Replacement in Engine Controls - 8.1L or to the Cat© Medium Duty Diesel Manual - LG5. 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 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2