P2C31

Turbocharger/Supercharger Intake Air Flow Control Circuit Open

P2C31 is a generic OBD-II powertrain diagnostic trouble code: Turbocharger/Supercharger Intake Air Flow Control Circuit Open. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P2C31
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P2C31 means

P2C31 is stored when the ECM detects an open circuit in the intake air flow control actuator circuit. This actuator is part of the turbocharger or supercharger induction system and may govern a swirl flap, charge air bypass valve, or similar variable-geometry intake component designed to optimise air charge motion and volumetric efficiency across different operating conditions.

An open circuit prevents the ECM from commanding the actuator, which may result in the intake system being locked in its default mechanical position. Depending on design, this could limit low-end torque, reduce high-rpm power, or affect exhaust gas recirculation compatibility. The MIL is set and a pending code becomes confirmed after the required number of failed drive cycles.

The diagnostic approach mirrors other open-circuit actuator faults: check supply voltage, ground continuity, harness integrity, and actuator coil resistance. Intake manifold-mounted actuators are especially vulnerable to oil contamination from crankcase ventilation and to carbon build-up that can increase actuator load and accelerate electrical failure.

Common causes

Most-frequently reported root causes when P2C31 is logged.

  • 1
    Open or broken wire in the intake air flow control actuator supply or ground circuit.
  • 2
    Corroded connector terminals at the actuator or along the harness.
  • 3
    Failed intake air flow control actuator with an open internal motor or solenoid winding.
  • 4
    Blown fuse protecting the intake actuator circuit.
  • 5
    ECM output driver failure on the intake air flow control output.
  • 6
    Wiring damage from oil contamination or heat near the intake manifold.
  • 7
    Connector seal failure leading to moisture ingress and terminal oxidation.

Symptoms drivers notice

MIL illuminated.
Reduced low-speed torque or altered engine breathing characteristics.
Slight hesitation or flat spot at specific engine speeds.
No perceptible symptom in some vehicles if the default position is close to optimal.
Possible increased exhaust emissions at idle or light load.

How to diagnose P2C31

A typical diagnostic flow when this code is present.

  1. 1
    Read all stored codes and freeze-frame data with a scan tool.
  2. 2
    Inspect the intake air flow control actuator connector and wiring for damage, oil contamination, or corrosion.
  3. 3
    Measure actuator resistance at the unplugged connector; an open reading confirms winding failure.
  4. 4
    Check for supply voltage and ground at the connector with the ignition on.
  5. 5
    Perform a continuity test on the harness between the ECM and the actuator connector.
  6. 6
    Attempt ECM actuator activation via scan tool bidirectional control while monitoring circuit current.
  7. 7
    Replace damaged wiring, connectors, or actuator based on findings; clear codes and verify repair.

Vehicles where we've handled P2C31

Platforms in our catalogue with confirmed P2C31 coverage.

MB AMG GLE53
2020
MB AMG GLE53 (W167)
2020

Related powertrain codes

Frequently asked questions

What does the intake air flow control actuator do?

It adjusts a valve or flap inside the intake manifold or induction tract to change air charge motion (swirl or tumble) or bypass pathways, optimising combustion efficiency at different speeds and loads.

Is P2C31 serious?

It is typically a warning-level fault. Performance impact varies by design, but the MIL will remain on and emissions may increase until the fault is repaired.

Can carbon build-up cause P2C31?

Carbon or oil deposits can mechanically seize the valve, causing the actuator motor to stall and eventually fail electrically. Inspect the valve for mechanical freedom as part of diagnosis.

Will P2C31 cause a failed emissions test?

Because the MIL is illuminated, the vehicle will fail an OBD-based emissions inspection in most jurisdictions regardless of measured tailpipe emissions.

Disabling P2C31 in software

RaceTune can permanently disable P2C31 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

ECUs with a P2C31 disable in our catalogue

Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.

  • Bosch MG1CP002 verified 1 software version

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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