What causes fault code P0511?

• Most likely: Faulty Idle Air Control (IAC) valve - internal short or open circuit in the solenoid • Likely: Damaged wiring or corroded connectors leading to the IAC valve • Possible: Excessive carbon buildup causing mechanical binding, leading to electrical circuit stress • Rare: Internal PCM failure in the IAC driver circuit

How do you fix fault code P0511?

Visual Inspection: Inspect the IAC valve connector for corrosion and check the wiring harness for signs of rubbing or breakage. Cleaning: Remove the IAC valve and clean any carbon buildup from the plunger and passages using throttle body cleaner. Resistance Test: Use a multimeter to measure the IAC valve internal resistance. Typical values are 8-20 Ohms; an O.L. or 0 Ohm reading indicates a failed solenoid. Signal Test: Check for 12V power at the harness and verify the PCM control signal using an oscilloscope or a high-quality scan tool's live data. Replacement: If the component fails electrical tests, replace the IAC valve and perform an idle relearn procedure if required by the manufacturer.

Powertrain (Engine & Gearbox)Standard EOBD

P0511 - Idle Air Control (IAC) System Circuit

Q: What are the symptoms of fault code P0511?

• Check engine light (MIL) illuminated • Engine stalls at idle or when coming to a stop • Erratic or abnormally high/low idle speed • Difficult to start unless throttle is depressed slightly • Vehicle may fail emissions testing due to the active DTC

Last updated:1 February 2026

Related:IAC-ventil (Idle Air Control), Throttle Body, Powertrain Control Module (PCM/ECM), Kablage och kontaktstycken, MAF Sensor

System

Powertrain (Engine & Gearbox)

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Technical Description

P0511 is a generic OBD-II diagnostic trouble code (DTC) indicating a circuit malfunction in the Idle Air Control (IAC) system. The PCM monitors the IAC circuit to ensure the valve responds correctly to commands for maintaining target idle RPM. The IAC valve bypasses air around the closed throttle plate. If the PCM detects an out-of-range electrical signal—such as an open circuit, high resistance, or a short—it will trigger P0511. Modern 'Drive-by-Wire' systems may use the electronic throttle body for this function, but P0511 specifically refers to systems utilizing a dedicated IAC motor/valve.

Possible Causes

Faulty Idle Air Control (IAC) valve - internal short or open circuit in the solenoid

Damaged wiring or corroded connectors leading to the IAC valve

Excessive carbon buildup causing mechanical binding, leading to electrical circuit stress

Internal PCM failure in the IAC driver circuit

Symptoms

Check engine light (MIL) illuminated

Engine stalls at idle or when coming to a stop

Erratic or abnormally high/low idle speed

Difficult to start unless throttle is depressed slightly

Vehicle may fail emissions testing due to the active DTC

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P0511 - Idle Air Control (IAC) System Circuit

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P0511 - Idle Air Control (IAC) System Circuit

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Symptoms

Recommended Solution

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