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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

BMW 3 Series

See BMW-specific causes & cost
Volkswagen

P0502 on Volkswagen

Volkswagen Golf

See Volkswagen-specific causes & cost
Ford

P0502 on Ford

Ford Focus

See Ford-specific causes & cost
Opel

P0502 on Opel

Opel Astra

See Opel-specific causes & cost

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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Scan your car with Skanyx to diagnose P0502

Your car logged P0502. Skanyx reads it on any standard Bluetooth OBD2 adapter, tells you whether it is safe to keep driving, and shows the €60-€650 repair range so you know the number before a shop quotes you.

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