Speedometer and/or Odometer Inaccurate or Inoperative

Speedometer and/or Odometer Inaccurate or Inoperative

Diagnostic Fault Information

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

Circuit/System Description

The instrument panel cluster (IPC) displays the vehicle speed based on the information from the body control module (BCM). The engine control module (ECM) sends the vehicle speed signal information via the GMLAN serial data circuit to the BCM. The BCM sends a GMLAN message to the IPC indicating the vehicle speed. The IPC displays the vehicle speed based on the GMLAN serial data message from the BCM.

Circuit/System Testing

Important: The drive wheels of the vehicle must be raised and the transmission must be placed in drive or first gear.

1. Start the engine, raise the vehicle drive wheels and place the transmission in drive or first gear. Verify that the speedometer value matches the scan tool Vehicle Speed parameter in the ECM Engine Data List.

• If the speedometer is incorrect, test or replace the IPC.

Repair Instructions

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

Control Module References for IPC replacement, setup, and programming