What does it mean?
P1540 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Vehicle Speed Sensor Malfunction 2 .
Symptoms
- Check engine light on with an erratic or dead speedometer
- Cruise control disabled and unable to set
- Harsh, delayed or incorrect automatic gear changes
- ABS and traction control warning lamps on as well
- Odometer not counting or counting inconsistently
- Idle drops or the engine stalls when coming to a stop
Likely causes
- Failed vehicle speed sensor or the wheel speed sensor that supplies the signal
- Metal debris on the sensor tip or damaged teeth on the reluctor ring
- Open or shorted signal wire between the sensor and the module
- Corroded connector at the gearbox, exposed to oil, heat and road spray
- Non-standard tyre size or a changed final drive ratio, so the two speed sources no longer agree
- Fault in the module that shares the speed signal, such as the ABS control unit
- Receiving module input circuit failure
How to fix it
- Compare the vehicle speed value in live data with the individual wheel speeds and with the actual road speed on a test drive
- Inspect the sensor tip for metal debris and the reluctor ring for damaged or missing teeth
- Measure the sensor resistance or check its output signal while the wheel or shaft is turned
- Inspect the connector at the gearbox for oil, corrosion and loose terminals
- Check the signal wire for continuity, short to ground and short to voltage
- Replace the speed sensor if the signal is missing or unstable
- Check the ABS module and its wheel speed inputs when several wheel speed values are wrong, and confirm the tyre and gearing data match the vehicle