P2C20

Turbocharger/Supercharger Boost Control A Circuit Open

P2C20 is a generic OBD-II powertrain diagnostic trouble code: Turbocharger/Supercharger Boost Control A 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
P2C20
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P2C20 means

P2C20 is set when the ECM/PCM detects an open circuit condition in the boost control actuator circuit designated as circuit A. This actuator is typically a solenoid or stepper motor responsible for controlling turbocharger wastegate position or variable-geometry vane position to regulate manifold boost pressure.

An open circuit means the ECM is commanding the actuator but receiving no current feedback, or the circuit voltage is outside the expected operating range for an energised load. This prevents the ECM from controlling boost, which usually causes the system to default to a safe low-boost or no-boost condition to protect the engine and turbocharger from over-boost damage.

The fault may originate anywhere along the wiring harness between the ECM and the actuator, including connector pins, inline splices, or the actuator winding itself. Intermittent opens caused by chafed wires or corroded connectors are common and may set the code only under vibration or heat.

Common causes

Most-frequently reported root causes when P2C20 is logged.

  • 1
    Open or broken wire in the boost control actuator A feed or ground circuit.
  • 2
    Corroded, backed-out, or spread terminal in the actuator harness connector.
  • 3
    Failed boost control solenoid with an open internal winding.
  • 4
    Blown fuse supplying power to the boost control actuator circuit.
  • 5
    ECM/PCM internal driver fault on the boost control A output pin.
  • 6
    Chafed wiring contacting chassis ground intermittently breaking the circuit.
  • 7
    Connector moisture intrusion causing high resistance that triggers open-circuit detection.

Symptoms drivers notice

MIL (Check Engine light) illuminated.
Reduced engine power or limp-home mode with restricted boost.
Sluggish acceleration and poor throttle response.
Possible black smoke or rich running if boost defaults to zero.
Audible change in turbocharger noise under load.

How to diagnose P2C20

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool, record all stored codes and freeze-frame data before clearing.
  2. 2
    Check for related boost pressure sensor or actuator codes that may point to the root cause.
  3. 3
    Inspect the boost control actuator connector and wiring for visible damage, corrosion, or loose terminals.
  4. 4
    Measure actuator solenoid resistance at the connector; compare to manufacturer specification.
  5. 5
    Check supply voltage and ground integrity at the actuator connector with the ignition on.
  6. 6
    Perform a wiggle test on the harness while monitoring circuit voltage live to locate intermittent opens.
  7. 7
    If wiring and connector are sound, substitute or bench-test the actuator before suspecting ECM driver failure.

Vehicles where we've handled P2C20

Platforms in our catalogue with confirmed P2C20 coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

Can I drive with P2C20 active?

Short distances at reduced load are generally possible, but the engine will likely be in limp mode with limited boost. Prolonged driving risks poor fuel economy and potential engine stress; repair promptly.

Will clearing the code make P2C20 go away?

Clearing the code removes it temporarily, but it will return as soon as the ECM runs the boost control diagnostic and detects the open circuit again unless the underlying fault is repaired.

Is the boost control actuator the same as the wastegate solenoid?

On many turbocharged engines they are the same component, but on variable-geometry turbos the actuator may control the VGT vanes instead of a wastegate. Check the vehicle-specific wiring diagram.

Could a bad ECM cause P2C20?

ECM driver failure is possible but uncommon. Always verify wiring, connectors, and the actuator itself before suspecting the ECM, as misdiagnosis is costly.

Disabling P2C20 in software

RaceTune can permanently disable P2C20 — 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 P2C20 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 EDC17C50 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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