P0502 means the ECU is detecting a voltage on the vehicle speed sensor circuit that is lower than expected, typically because the signal wire is shorted to ground, the sensor has failed open, or the connector has lost contact. On vehicles that use the ABS wheel speed sensors as the primary speed input, P0502 usually accompanies an ABS wheel speed code.
DTC/P0502·BMW
P0502 on BMW: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeverityNot safe to driveBMW
P0502 on a BMW means the ECU is detecting a voltage on the vehicle speed sensor circuit that is lower than expected, typically because the signal wire is shorted to ground, the sensor has failed open, or the connector has lost contact. On vehicles that use the ABS wheel speed sensors as the primary speed input, P0502 usually accompanies an ABS wheel speed code.
Repair cost on BMW€84 - €910
What does P0502 mean on a BMW?
BMW 3 Series
2005-2024On E90 and F30 3 Series, P0502 typically follows a complete ABS wheel speed sensor failure, often at the rear axle. Iron particles from the bearing collect on the sensor magnet and eventually short the signal to ground. BMW recommends inspecting the bearing whenever a rear sensor is replaced.
What causes P0502 on a BMW?
Beyond the generic causes listed on the main P0502 page, these are the BMW-specific patterns we see most often:
BMW 3 SeriesRear ABS wheel speed sensor failure with short to ground
BMW 3 SeriesIron debris from worn rear bearing contaminating the sensor
How to diagnose P0502 on a BMW with OBD2
Follow these steps to pinpoint the root cause of P0502:
- Read all stored codes. Companion ABS wheel speed codes (C-codes) usually point directly to the failed circuit
- Locate the suspect sensor and inspect the connector for water, corrosion, and damaged pins. Reseat the connector and clear the code to see if it returns
- With ignition off, measure resistance from the sensor signal pin to chassis ground. A near-zero reading confirms a short to ground in the wiring or the sensor
- Backprobe the sensor connector with the engine running and the wheels spinning. A Hall-effect sensor should switch between roughly 0 V and 5 V; a magnetic sensor should produce a small AC waveform that grows with speed
- If the wiring and sensor are healthy, inspect the reluctor ring for missing teeth, cracks, or a sheared press fit
How much does P0502 cost to fix on a BMW? (EUR)
Estimated repair costs on a BMW (BMW parts and labour typically run 40% above the average for this code).
Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0502 on BMW
These codes commonly cluster with P0502 on BMW vehicles:
FAQ: P0502 on BMW
What does low input on a speed sensor circuit actually mean?
It means the ECU is seeing a voltage that is below the normal range on the signal wire, usually because the wire is shorted to ground, the sensor has failed open, or the connector is disconnected. The ECU interprets this as no movement and triggers P0502.
Why is my speedometer stuck at zero?
The most common cause is a dead vehicle speed or ABS wheel speed sensor, or a broken signal wire between the sensor and the ECU. On cars that share the ABS signal with the speedometer, a single failed sensor can knock out both.
Can I drive a short distance with P0502?
Mechanically yes, but the speedometer will not work and ABS plus traction control will be disabled. That makes it illegal to drive on public roads in most EU countries. Drive only as far as needed to reach a workshop and keep speeds low.
Is P0502 always a sensor problem?
No. Wiring damage is just as common, especially where the harness runs through the wheel arch or near the gearbox. Always test the wiring before replacing the sensor or you may swap parts without fixing the fault.
Looking for the full P0502 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0502 guideSkanyx · BMW
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