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P0502: Vehicle speed sensor circuit low input

The ECU sees too low a speed signal, or none, with the car moving. Usually the connector, a broken or earthed wire, or the sensor itself.

Code P0502 at a glance
CodeP0502
SystemEngine and transmission
GroupP05xx, Speed, idle and auxiliary inputs
TypeGeneric: it means the same on every make
Can you keep driving?With care

What P0502 means

The speed sensor sends a signal that rises with road speed. Low input means the ECU sees a value below what should be possible, often zero even though the car is moving. It is nearly always an electrical fault: wire, connector, earth or the sensor.

Most common causes

  • Speed sensor connector unplugged or corroded
  • Signal wire broken or shorted to earth
  • Faulty speed sensor
  • Fault in an ABS wheel sensor or module, where the speed comes from there

Symptoms

  • Speedometer at zero or dropping out
  • Automatic gearbox not shifting properly
  • Cruise control not working
  • Unstable idle when stopping
  • Engine warning light on

Can you drive with P0502?

With care You can drive with care, but with no speedometer and the gearbox or idle possibly affected. Take it to a garage soon.

How to check it

Watch live vehicle speed while someone else drives. If it shows zero on the move, check the sensor connector and, on cars that take speed from the ABS, look for ABS fault codes.

How to read and clear P0502 with Final OBD

Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0502 with this same explanation and whether it’s confirmed, pending or permanent.

With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.

Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.

Similar codes

P0502 is a generic code, so it means the same on any make, for example on Alfa Romeo, Dacia, Kia, Nissan, Opel / Vauxhall, Škoda. See what Final OBD does on your car in makes and models.

What does code P0502 mean?

The speed sensor sends a signal that rises with road speed. Low input means the ECU sees a value below what should be possible, often zero even though the car is moving. It is nearly always an electrical fault: wire, connector, earth or the sensor.

Can you drive with P0502?

You can drive with care, but with no speedometer and the gearbox or idle possibly affected. Take it to a garage soon.

How do you clear P0502?

With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0502 comes back.