Tachometer Inaccurate or Inoperative

TACHOMETER INACCURATE OR INOPERATIVE

DIAGNOSTIC FAULT INFORMATION

IMPORTANT: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Testing and Inspection

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) converts the data from the engine speed sensor to a 2 pulses/engine revolution signal. The 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. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. With the scan tool, under Special Functions, perform the IPC gage sweep test.
- If the tachometer gage does not sweep from its low to high position, replace the IPC.

REPAIR INSTRUCTIONS

IMPORTANT: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

Control Module References for IPC replacement, setup, and programming