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DTC/P0502

P0502: Vehicle Speed Sensor "A" Circuit Low Input

Quick Answer
Moderate SeverityNot safe to driveElectrical

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.

Estimated repair costFrom €60 to €650+, varies by vehicle

What does P0502 mean?

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.

P0502 is a electrical-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0502 and illuminates the check engine light.

What are the symptoms of P0502?

If your vehicle has triggered P0502, you may notice one or more of these symptoms:

  • Speedometer reads zero even while driving
  • ABS and traction control warning lights on
  • Cruise control will not engage
  • Automatic transmission shifts harshly or stays in a single gear
  • Check engine light on

What causes P0502?

Here are the most common causes of P0502, ranked by how likely they are to be the culprit:

highOpen or shorted-to-ground wiring on the speed sensor signal circuit
highFailed vehicle speed or ABS wheel speed sensor
mediumDisconnected or corroded sensor connector
lowMissing or sheared reluctor ring

Is it safe to drive with P0502?

No - address this immediately. The ECU is reading a vehicle speed signal that is below the expected threshold, which usually means zero signal or a shorted-to-ground circuit. Speedometer, ABS, and transmission shift quality are affected. Drive only as far as needed to reach a workshop.

How do you diagnose P0502?

Follow these steps to pinpoint the root cause of P0502:

  1. Read all stored codes. Companion ABS wheel speed codes (C-codes) usually point directly to the failed circuit
  2. 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
  3. 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
  4. 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
  5. 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?

Repair costs for P0502 vary depending on the root cause and your vehicle. Here are typical estimates:

Repair Parts Cost Labor Cost Total Estimate DIY Difficulty
Repair sensor wiring or connector €10–€40 €50–€150 €60–€190 Moderate
Replace vehicle speed or ABS wheel speed sensor €30–€120 €40–€100 €70–€220 Moderate
Replace wheel bearing with integrated reluctor ring €80–€250 €150–€400 €230–€650 Professional

Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.

P0502 on specific vehicles

P0502 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:

BMW

P0502 on BMW 3 Series

2005-2024

On 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 3 Series?

BMW 3 SeriesRear ABS wheel speed sensor failure with short to ground
BMW 3 SeriesIron debris from worn rear bearing contaminating the sensor

P0502 repair cost for BMW 3 Series

Estimated costs for BMW 3 Series ownersadjusted higher than average due to BMW-specific parts pricing

Repair Parts Cost Labor Cost Total Estimate DIY Difficulty
Repair sensor wiring or connector €14–€56 €70–€210 €84–€266 Moderate
Replace vehicle speed or ABS wheel speed sensor €42–€168 €56–€140 €98–€308 Moderate
Replace wheel bearing with integrated reluctor ring €112–€350 €210–€560 €322–€910 Professional

Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.

Volkswagen

P0502 on Volkswagen Golf

2003-2024

Mk5 and Mk6 Golf are prone to rear ABS sensor harness chafing along the trailing arm. Once the insulation rubs through, the signal wire shorts to body metal and P0502 sets immediately. Replacing the wiring sleeve and rerouting the harness is the proper repair.

What causes P0502 on a Volkswagen Golf?

Volkswagen GolfRear ABS sensor wire chafed through to ground on Mk5/Mk6
Volkswagen GolfConnector pin push-out at the front sensor after suspension work

P0502 repair cost for Volkswagen Golf

Estimated costs for Volkswagen Golf ownersadjusted higher than average due to Volkswagen-specific parts pricing

Repair Parts Cost Labor Cost Total Estimate DIY Difficulty
Repair sensor wiring or connector €12–€46 €57–€173 €69–€218 Moderate
Replace vehicle speed or ABS wheel speed sensor €35–€138 €46–€115 €81–€253 Moderate
Replace wheel bearing with integrated reluctor ring €92–€288 €173–€460 €265–€747 Professional

Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.

Ford

P0502 on Ford Focus

2005-2022

Mk2 and Mk3 Focus suffer rear bearing magnetic encoder failures. When the encoder ring inside the bearing demagnetises or cracks, the sensor stops producing a signal entirely and the ECU logs P0502. The fix is a new rear bearing assembly with integrated ring.

What causes P0502 on a Ford Focus?

Ford FocusRear bearing magnetic encoder ring failure on Mk2/Mk3
Ford FocusFront sensor connector water ingress in salt climates

P0502 repair cost for Ford Focus

Estimated costs for Ford Focus ownersadjusted lower than average due to Ford-specific parts pricing

Repair Parts Cost Labor Cost Total Estimate DIY Difficulty
Repair sensor wiring or connector €9–€36 €45–€135 €54–€171 Moderate
Replace vehicle speed or ABS wheel speed sensor €27–€108 €36–€90 €63–€198 Moderate
Replace wheel bearing with integrated reluctor ring €72–€225 €135–€360 €207–€585 Professional

Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.

Opel

P0502 on Opel Astra

2009-2021

Astra J commonly logs P0502 after a front wheel speed sensor takes water through its connector. The signal pin corrodes and eventually loses contact entirely, presenting as a low circuit fault. Cleaning may revive the connection briefly but a sensor and pigtail replacement is the durable fix.

What causes P0502 on a Opel Astra?

Opel AstraFront sensor pin corrosion on Astra J
Opel AstraRear sensor wiring damage near torsion beam mount

P0502 repair cost for Opel Astra

Estimated costs for Opel Astra ownersadjusted lower than average due to Opel-specific parts pricing

Repair Parts Cost Labor Cost Total Estimate DIY Difficulty
Repair sensor wiring or connector €9–€34 €43–€128 €51–€162 Moderate
Replace vehicle speed or ABS wheel speed sensor €26–€102 €34–€85 €60–€187 Moderate
Replace wheel bearing with integrated reluctor ring €68–€213 €128–€340 €196–€553 Professional

Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.

These codes are often seen alongside P0502 or indicate related issues:

P0500P0501P0503P0720C0040

Common questions about P0502

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.

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