Tachometer Inaccurate or Inoperative

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

Circuit/System Testing

1. Ignition ON, with the scan tool, perform the IPC Gage Sweep Test in the IPC Output Controls. Verify that all gage dials move from minimum to the maximum value and back to the gage minimum value.

• If the tachometer does not perform the IPC Gage Sweep Test, 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