The engine control module (ECM)/powertrain control module (PCM) creates the engine speed signal by pulsing the signal circuit to ground at the rate of 2 pulses per engine revolution. The instrument panel cluster (IPC) converts the signal to a tachometer position. The IPC also receives a serial data message from the ECM/PCM indicating the engine speed.

Schematic Reference

Instrument Cluster Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Instrument Cluster Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Ignition OFF, disconnect the harness connector at the ECM/PCM. Install a signal generator and instrument panel tester between ground and the following engine speed signal circuit:

•	Terminal 28 (LF8)

•	Terminal 38 LF6)

•	Terminal 10 (L18)

2. Ignition ON, set the signal generator to generate a tachometer signal. Verify that the tachometer indicates an RPM reading.

⇒	If no RPM reading is present, test the signal circuit for an open/high resistance, a short to voltage, or a short to ground. If the circuit tests normal, replace the IPC.

3. If all circuits test normal, test or replace the ECM/PCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for the ECM/PCM and IPC replacement, setup, and programming