B0540

DTC B0540

Diagnostic Instructions

* Perform The Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B0540
- Speedometer Circuit

Diagnostic Fault Information






Circuit/System Description

The engine control module (ECM) creates the vehicle speed signal by pulsing the vehicle speed signal circuit to ground at a rate of 4 KPPM. The instrument panel cluster (IPC) converts the 4 KPPM vehicle speed signal to a speedometer position to indicate the vehicle speed. The vehicle speed sensor (VSS) input is pulled high to B+ in the instrument panel cluster (IPC). The IPC also receives from the ECM a class 2 message indicating the vehicle speed. The IPC uses the class 2 vehicle speed information from the ECM for diagnostics purposes.

Conditions for Running the DTC

* The IPC receives a class 2 message from the ECM indicating that the vehicle speed is greater than 10 km/h (6 mph)
* The ignition voltage is between 9-18 volts.

Conditions for Setting the DTC

* The IPC does not detect a 4 KPPM signal on the vehicle speed signal circuit.
* The above condition must be present for a minimum of 5 seconds.

Action Taken When the DTC Sets

The IPC stores DTC B0540 in memory.

Conditions for Clearing the DTC

* The DTC becomes history when the conditions for setting the DTC are no longer present.
* The history DTC clears after 40 malfunction-free warm-up cycles.

Circuit/System Testing

1. Ignition ON, with the scan tool perform the IPC Gage Sweep Test in the IPC Output Controls. Verify the speedometer dial moves from the minimum to the maximum position and back to the speedometer minimum position.

• If the speedometer does not perform the IPC Gage Sweep Test, replace the IPC.

2. Ignition OFF disconnect the C1 harness connector at the ECM.
3. Ignition ON, test for 9-11 volts between the vehicle speed signal circuit terminal 39 and ground.

• If less than 9 volts, test the vehicle speed signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the IPC.

• If greater than 11 volts, test the vehicle speed signal circuit for a short to voltage.

4. If all circuits test normal, test or replace the ECM.

Repair Instructions

Perform The Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

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