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DTC/P0502

P0502: Vehicle Speed Sensor "A" Circuit Low Input

Quick Answer
Moderata GravitàNon sicuro da guidareImpianto elettrico

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.

Costo di riparazione stimatoDa €60 a €650+, varia in base al veicolo

Cosa significa P0502?

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 è un codice diagnostico di guasto relativo a impianto elettrico, classificato con gravità moderate. Quando la centralina (ECU) del tuo veicolo rileva questa condizione, memorizza P0502 e accende la spia motore.

Quali sono i sintomi di P0502?

Se il tuo veicolo ha attivato P0502, potresti notare uno o più di questi sintomi:

  • 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

Cosa causa P0502?

Ecco le cause più comuni di P0502, ordinate in base alla probabilità che siano la causa del problema:

altaOpen or shorted-to-ground wiring on the speed sensor signal circuit
altaFailed vehicle speed or ABS wheel speed sensor
mediaDisconnected or corroded sensor connector
bassaMissing or sheared reluctor ring

È sicuro guidare con P0502?

No, risolvi subito il problema. 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.

Come si diagnostica P0502?

Segui questi passaggi per individuare la causa principale di 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

Quanto costa riparare P0502?

I costi di riparazione di P0502 variano a seconda della causa principale e del tuo veicolo. Ecco le stime tipiche:

Riparazione Costo dei ricambi Costo della manodopera Stima totale Difficoltà fai-da-te
Repair sensor wiring or connector €10–€40 €50–€150 €60–€190 Moderata
Replace vehicle speed or ABS wheel speed sensor €30–€120 €40–€100 €70–€220 Moderata
Replace wheel bearing with integrated reluctor ring €80–€250 €150–€400 €230–€650 Professionale

Prezzi stimati al March 2026. I costi variano in base alla regione, al veicolo e all'officina.

P0502 su veicoli specifici

P0502 si comporta in modo diverso a seconda del tuo veicolo. Seleziona la tua auto qui sotto per cause specifiche del modello, problemi noti e stime dei costi adeguate:

BMW

P0502 su 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.

Cosa causa P0502 su una 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

Costo di riparazione di P0502 per BMW 3 Series

Costi stimati per i proprietari di BMW 3 Seriesadeguato al rialzo rispetto alla media a causa dei prezzi dei ricambi specifici BMW

Riparazione Costo dei ricambi Costo della manodopera Stima totale Difficoltà fai-da-te
Repair sensor wiring or connector €14–€56 €70–€210 €84–€266 Moderata
Replace vehicle speed or ABS wheel speed sensor €42–€168 €56–€140 €98–€308 Moderata
Replace wheel bearing with integrated reluctor ring €112–€350 €210–€560 €322–€910 Professionale

Prezzi stimati al March 2026. I costi variano in base alla regione, al veicolo e all'officina.

Volkswagen

P0502 su 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.

Cosa causa P0502 su una 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

Costo di riparazione di P0502 per Volkswagen Golf

Costi stimati per i proprietari di Volkswagen Golfadeguato al rialzo rispetto alla media a causa dei prezzi dei ricambi specifici Volkswagen

Riparazione Costo dei ricambi Costo della manodopera Stima totale Difficoltà fai-da-te
Repair sensor wiring or connector €12–€46 €57–€173 €69–€218 Moderata
Replace vehicle speed or ABS wheel speed sensor €35–€138 €46–€115 €81–€253 Moderata
Replace wheel bearing with integrated reluctor ring €92–€288 €173–€460 €265–€747 Professionale

Prezzi stimati al March 2026. I costi variano in base alla regione, al veicolo e all'officina.

Ford

P0502 su 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.

Cosa causa P0502 su una Ford Focus?

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

Costo di riparazione di P0502 per Ford Focus

Costi stimati per i proprietari di Ford Focusadeguato al ribasso rispetto alla media a causa dei prezzi dei ricambi specifici Ford

Riparazione Costo dei ricambi Costo della manodopera Stima totale Difficoltà fai-da-te
Repair sensor wiring or connector €9–€36 €45–€135 €54–€171 Moderata
Replace vehicle speed or ABS wheel speed sensor €27–€108 €36–€90 €63–€198 Moderata
Replace wheel bearing with integrated reluctor ring €72–€225 €135–€360 €207–€585 Professionale

Prezzi stimati al March 2026. I costi variano in base alla regione, al veicolo e all'officina.

Opel

P0502 su 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.

Cosa causa P0502 su una Opel Astra?

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

Costo di riparazione di P0502 per Opel Astra

Costi stimati per i proprietari di Opel Astraadeguato al ribasso rispetto alla media a causa dei prezzi dei ricambi specifici Opel

Riparazione Costo dei ricambi Costo della manodopera Stima totale Difficoltà fai-da-te
Repair sensor wiring or connector €9–€34 €43–€128 €51–€162 Moderata
Replace vehicle speed or ABS wheel speed sensor €26–€102 €34–€85 €60–€187 Moderata
Replace wheel bearing with integrated reluctor ring €68–€213 €128–€340 €196–€553 Professionale

Prezzi stimati al March 2026. I costi variano in base alla regione, al veicolo e all'officina.

Questi codici compaiono spesso insieme a P0502 o indicano problemi correlati:

P0500P0501P0503P0720C0040

Domande frequenti su 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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