Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using the diagnostic procedure. |
| • | 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 CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Vehicle Speed Signal | B0540 | B0540 | B0540 | -- |
Circuit Description
The engine control module (ECM) creates the vehicle speed signal by pulsing the vehicle speed signal circuit to ground at a rate of 4KPPM. The instrument panel cluster (IPC) converts the 4KPPM vehicle speed signal to a speedometer position to indicate the vehicle speed. The IPC also receives from the ECM a serial data message indicating the vehicle speed. The IPC uses the serial data vehicle speed information from the ECM for diagnostics purposes.
Conditions for Running the DTC
| • | The IPC receives a serial data 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 detects that the vehicle speed signal circuit does not match the vehicle speed from the 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). |
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. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Instrument Cluster Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the harness connector X1 at the ECM. Install a signal generator and instrument panel tester between the vehicle speed signal circuit terminal 39 and ground.
- Ignition ON, set the signal generator to generate a speedometer signal. Verify that the vehicle speedometer indicates a reading.
- Ignition OFF, disconnect the harness connector at the transmission control module (TCM).
- Ignition ON, test for 9 - 13 volts between the vehicle speed signal circuit terminal 5 and ground.
- If all circuits test normal, test or replace the TCM.
| ⇒ | If no speedometer reading is present, test the signal circuit for a short to voltage, a short to ground or an open/high resistance. If the circuit tests normal, replace the IPC. |
| ⇒ | If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal replace the ECM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for the ECM, TCM and IPC replacement, setup, and programming.
