Tachometer Inaccurate or Inoperative. GMC Truck Envoy

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2007 🢒 Envoy - 2WD 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Tachometer Inaccurate or Inoperative

Diagnostic Instructions

•	Perform the Diagnostic System Check - Vehicle prior to using the diagnostic procedure.

•	Review Strategy Based Diagnosis for an overview of the diagnostic approach.

•	Diagnostic Procedure Instructions provides an overview of each diagnostic category.

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

Reference Information

Schematic Reference

•	Instrument Cluster Schematics

•	Engine Controls Schematics for the 4.2L engine

•	Engine Controls Schematics for the 5.3L engine

•	Engine Controls Schematics for the 6.0L engine

Connector End View Reference

•	Displays and Gages Connector End Views

•	Powertrain Control Module Connector End Views

•	Engine Control Module Connector End Views for the 5.3L engine

•	Engine Control Module Connector End Views for the 6.0L engine

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

Scan Tool Data List

Circuit/System Testing

Ignition ON, engine ON, verify the scan tool engine speed parameter for the IPC matches the tachometer display.

⇒	If the engine speed parameter does not match the tachometer display, test the signal circuit for a high resistance.

If the circuit tests normal, replace the IPC.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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