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DTC/P0508

P0508: Idle Air Control System Circuit Low

Quick Answer
Moderata GravitàSicuro da guidare (a breve termine)Impianto elettrico

P0508 means the ECU is detecting a voltage on the idle air control valve circuit that is below the expected threshold. The most common cause is a short to ground in the wiring, but a failed valve coil or a corroded connector can produce the same symptom. This code applies to vehicles with a separate idle air control valve rather than fully electronic throttle bodies.

Costo di riparazione stimatoDa €45 a €1000+, varia in base al veicolo

Cosa significa P0508?

P0508 means the ECU is detecting a voltage on the idle air control valve circuit that is below the expected threshold. The most common cause is a short to ground in the wiring, but a failed valve coil or a corroded connector can produce the same symptom. This code applies to vehicles with a separate idle air control valve rather than fully electronic throttle bodies.

P0508 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 P0508 e accende la spia motore.

Quali sono i sintomi di P0508?

Se il tuo veicolo ha attivato P0508, potresti notare uno o più di questi sintomi:

  • Engine stalls at idle or when slowing to a stop
  • Idle RPM fluctuates wildly or stays very low
  • Engine may not idle without throttle input
  • Check engine light on
  • Possible no-start if the IAC valve sticks closed

Cosa causa P0508?

Ecco le cause più comuni di P0508, ordinate in base alla probabilità che siano la causa del problema:

altaIdle air control valve coil shorted internally
altaSignal wire shorted to ground
mediaCorroded or damaged valve connector
bassaECU driver circuit failure (rare)

È sicuro guidare con P0508?

In genere sì, per brevi tragitti. The ECU sees a voltage on the idle air control circuit that is lower than expected, typically because the circuit is shorted to ground. Idle behaviour will be erratic and stalling is likely. Fix promptly to avoid being stranded.

Come si diagnostica P0508?

Segui questi passaggi per individuare la causa principale di P0508:

  1. Read freeze-frame data and confirm the ECU sees the IAC circuit below threshold at the time of the fault
  2. Locate the IAC valve (usually mounted on or near the throttle body) and inspect the connector for corrosion, oil mist, and damaged pins
  3. Unplug the valve and measure resistance across the coil terminals per the manufacturer specification (commonly 6 to 15 ohms). A reading well below spec confirms a shorted coil
  4. With the valve unplugged, measure resistance from each connector pin to chassis ground. A near-zero reading on the signal wire indicates a wiring short
  5. If wiring and valve test good but the code returns, suspect the ECU driver circuit. Confirm with a known-good spare ECU before condemning the original

Quanto costa riparare P0508?

I costi di riparazione di P0508 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 wiring or connector at the IAC valve €5–€30 €40–€120 €45–€150 Moderata
Replace idle air control valve €60–€250 €40–€100 €100–€350 Moderata
Repair ECU driver circuit or replace ECU €200–€800 €80–€200 €280–€1000 Professionale

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

P0508 su veicoli specifici

P0508 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:

Toyota

P0508 su Toyota Camry

1997-2006

Older Camrys with the 5S-FE and 1MZ-FE use a stepper-motor IAC valve. The coil windings can short internally after extended heat soak, producing P0508. Replacement valves are widely available and the swap takes about 30 minutes once the air intake is off.

Cosa causa P0508 su una Toyota Camry?

Toyota CamryStepper-motor IAC coil short on 5S-FE
Toyota CamryConnector corrosion under the intake plenum
Volkswagen

P0508 su Volkswagen Golf

1998-2006

Mk4 Golf 1.8T (AGU, AWP) IAC valves frequently develop internal coil shorts after the bore packs with carbon and oil. The carbon increases mechanical load on the coil and accelerates winding failure. Replacing the valve without addressing PCV oil mist usually leads to a repeat failure.

Cosa causa P0508 su una Volkswagen Golf?

Volkswagen GolfCoil winding short after carbon-loaded operation on Mk4 1.8T
Volkswagen GolfPCV oil contamination at connector accelerating corrosion

Costo di riparazione di P0508 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 wiring or connector at the IAC valve €6–€35 €46–€138 €52–€173 Moderata
Replace idle air control valve €69–€288 €46–€115 €115–€402 Moderata
Repair ECU driver circuit or replace ECU €230–€920 €92–€230 €322–€1150 Professionale

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

Ford

P0508 su Ford Focus

2000-2007

Mk1 and early Mk2 Focus with the Zetec engine use a separate IAC valve that suffers connector contamination from oil mist and gradual coil resistance drop. P0508 is well documented and aftermarket valves are inexpensive.

Cosa causa P0508 su una Ford Focus?

Ford FocusIAC coil resistance drift on Zetec engine
Ford FocusOil-contaminated connector on early Mk2

Costo di riparazione di P0508 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 wiring or connector at the IAC valve €5–€27 €36–€108 €41–€135 Moderata
Replace idle air control valve €54–€225 €36–€90 €90–€315 Moderata
Repair ECU driver circuit or replace ECU €180–€720 €72–€180 €252–€900 Professionale

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

Honda

P0508 su Honda Civic

2001-2011

Honda Civics with the K20 and R18 family use an IACV that is generally reliable but can suffer wiring damage from the intake harness rubbing on the throttle cable bracket. The signal wire shorts to ground intermittently and the ECU sets P0508.

Cosa causa P0508 su una Honda Civic?

Honda CivicWiring short from chafing at the throttle cable bracket
Honda CivicIACV coil failure after 200,000 km

Costo di riparazione di P0508 per Honda Civic

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

Riparazione Costo dei ricambi Costo della manodopera Stima totale Difficoltà fai-da-te
Repair wiring or connector at the IAC valve €5–€27 €36–€108 €41–€135 Moderata
Replace idle air control valve €54–€225 €36–€90 €90–€315 Moderata
Repair ECU driver circuit or replace ECU €180–€720 €72–€180 €252–€900 Professionale

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

Questi codici compaiono spesso insieme a P0508 o indicano problemi correlati:

P0505P0506P0507P0509P0511

Domande frequenti su P0508

What does idle air control circuit low mean?

It means the ECU sees voltage on the valve control wire that is lower than the design range. This usually points to a short to ground in the wiring or a shorted coil inside the valve. The ECU cannot drive the valve properly, so idle becomes unstable.

Why does my car stall at every red light?

When the IAC valve cannot open to compensate for closed throttle, the engine starves of air at idle and stalls. P0508 specifically points to an electrical fault preventing the valve from working, not a mechanical clog.

Can I just clean the valve to fix P0508?

Cleaning helps when the valve is mechanically stuck, which is more typical of P0506. P0508 is an electrical fault, so cleaning rarely cures it. Check wiring and valve coil resistance first.

Is the IAC valve the same as the throttle body?

No. The IAC valve is a separate solenoid that bypasses air around a closed throttle plate to set idle speed. Most cars from the early 2000s onward replaced the IAC valve with a fully electronic throttle body that opens slightly at idle, which is why P0508 is mostly seen on older vehicles.

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