Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Engine RPM Signal | 1 | 1 | 1 | -- |
Tachometer Malfunction | ||||
Circuit/System Description
The engine control module (ECM) creates the engine speed signal. The engine speed is sent to the IPC over a discreet wire from the ECM. The instrument panel cluster (IPC) converts the signal to a tachometer position indicating the engine speed.
Diagnostic Aids
Before attempting to diagnose a tachometer malfunction diagnose any ECM DTCs or driveability concerns.
Reference Information
Schematic Reference
Connector End View Reference
Displays and Gages Connector End Views
Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Start the engine with the scan tool installed. Verify that the Engine Speed parameter in the ECM IPC Data list varies with the actual engine RPM.
| ⇒ | If the parameter displayed is not the correct value replace the ECM. |
Circuit/System Testing
- Ignition OFF, disconnect the harness connectors at the ECM and IPC.
- Test the engine speed signal circuit for infinite resistance between the ECM connector terminal and ground.
- Test the engine speed signal circuit for less than 2 Ω between the ECM connector terminal and the IPC connector terminal.
- If all circuits test normal, replace the IPC.
| ⇒ | If not the specified value, repair the signal circuit for a short to ground. |
| ⇒ | If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for IPC or ECM replacement, setup and programming
