DTC Descriptor
DTC B0540: Speedometer CircuitDiagnostic Fault Information
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Vehicle Speed Signal Circuit | B0540 | B0540 | B0540 | -- |
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. |
Reference Information
Schematic Reference
| • | Engine Controls Schematics for the 4.2L engine |
| • | Engine Controls Schematics for the 5.3L engine |
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the ECM/PCM. Install a signal generator and instrument panel tester between the vehicle speed signal circuit and ground.
- Ignition ON, set the signal generator to generate a speedometer signal. Verify that the vehicle speedometer indicates a reading.
- If all circuits test normal, test or replace the ECM/PCM.
| ⇒ | 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. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for the ECM/PCM and IPC replacement, setup, and programming
