Tachometer: Testing and Inspection

Tachometer Inaccurate or Inoperative

Diagnostic Instructions
^ Perform the [Diagnostic System Check - Vehicle Diagnostic Information] prior to using this diagnostic procedure. Diagnostic System Check - Vehicle Diagnostic Information
^ Review [Strategy Based Diagnosis] for an overview of the diagnostic approach. Strategy Based Diagnosis
^ [Diagnostic Procedure Instructions - Vehicle Diagnostic Information]. Diagnostic Procedure Instructions - Vehicle Diagnostic Information

Circuit/System Description
The instrument panel cluster (IPC) displays the engine speed based on the information from the engine control module (ECM). The ECM converts the data from the engine speed sensor to a 2 pulses/engine revolution signal. The ECM sends the engine speed information via high speed GMLAN serial data circuit to the body control module (BCM). The BCM then sends the information via low speed GMLAN to the IPC to order to display the engine speed.

Circuit/System Testing
Ignition ON, engine ON, verify the scan tool Engine Speed parameter matches the tachometer display.
^ If the Engine Speed parameter does not match the tachometer display, replace the IPC.

Repair Instructions
Perform the [Diagnostic Repair Verification - Vehicle Diagnostic Information] after completing the diagnostic procedure. Diagnostic Repair Verification - Vehicle Diagnostic Information
[Control Module References] for IPC replacement, setup, and programming Programming and Relearning