Diagnostic Instructions
DTC Descriptor
DTC B0540: Speedometer Circuit
Diagnostic Fault Information
Circuit
| Short to Ground
| Open/High Resistance
| Short to Voltage
|
Vehicle Speed Signal Circuit
| B0540
| B0540
| B0540
|
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 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 does not detect a 4KPPM signal on the vehicle speed signal circuit. |
| • | The condition above 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. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Scan Tool Data List
Circuit/System Testing
- Ignition ON, the scan tool installed, 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. |
- Ignition OFF, disconnect the C1 harness connector at the ECM.
- Ignition ON, test for 9-11 volts between the vehicle speed signal circuit terminal 57 and ground.
| ⇒ | If less than 9 volts, test the vehicle speed signal circuit terminal 57 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 terminal 57 for a short to voltage. |
- If all circuits test normal, test or replace the ECM.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
Control Module References
for the ECM or IPC replacement, setup and programming
