Speedometer and/or Odometer Inaccurate or Inoperative

Speedometer and/or Odometer Inaccurate or Inoperative (4.2L Engine)

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview

Circuit Description

The instrument panel cluster (IPC) receives the vehicle speed information from the powertrain control module (PCM) through the vehicle speed signal circuit. The PCM converts the data from the vehicle speed sensor to a 4,000 pulses/mile signal. The PCM also sends a class 2 message to the IPC indicating the vehicle speed.

Circuit/System Testing

1. Ignition ON, perform the segments test with the scan tool.

• If not all of the segments illuminate, replace the IPC.

2. Raise the vehicle drive wheels. Refer to Lifting and Jacking the Vehicle.
3. Ignition ON, engine ON, transmission in Drive, verify the scan tool Vehicle Speed Sensor parameter in the IPC matches the speedometer display.

• If the Vehicle Speed Sensor parameter does not match the speedometer display, test the vehicle speed signal circuit for a high resistance.

4. If the circuit tests normal, test or replace the IPC.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

Control Module References for the IPC replacement, setup, and programming