B0540

DTC B0540

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using the 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 Description

The instrument panel cluster (IPC) receives the vehicle speed information from the engine control module (ECM)/powertrain control module (PCM) through the vehicle speed signal circuit. The ECM/PCM converts the data from the vehicle speed sensor to a 4000 pulses/mile signal. The ECM/PCM also sends a class 2 message to the IPC indicating the vehicle speed. If the IPC determines there is a loss of the vehicle speed signal from the ECM/PCM due to a vehicle speed signal circuit malfunction, a DTC sets.

Conditions for Running the DTC

* The vehicle speed is more than 10 km/h (6 mph).
* The ignition voltage is between 9-18 volts.

Conditions for Setting the DTC

* The IPC detects that the vehicle speed signal circuit does not match the vehicle speed from the class 2 serial data circuit.
* The condition above must be present for a minimum of 5 seconds.

Action Taken When the DTC Sets

* The IPC stores a DTC B0540 in memory.
* The speedometer defaults to 0 km/h (0 mph).
* No driver warning message will be displayed for this DTC.

Conditions for Clearing the DTC

* The history DTC clears after 100 malfunction-free warm-up cycles.
* The DTC becomes history when the conditions for setting the DTC are no longer present.
* The IPC receives the clear code command from the scan tool.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector X1 at the ECM/PCM. Install a signal generator and instrument panel tester between the following vehicle speed signal circuit and ground:

* Terminal 21 (4.2L)
* Terminal 39 (5.3L/6.0L)

2. Ignition ON, set the signal generator to generate a speedometer signal. Verify that the vehicle speedometer indicates a reading.

^ If no speedometer 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.

Repair Instructions

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