P2C2C

Turbocharger/Supercharger Boost Control B Circuit Low

P2C2C is a generic OBD-II powertrain diagnostic trouble code: Turbocharger/Supercharger Boost Control B Circuit Low. 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
P2C2C
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P2C2C means

P2C2C is set when the ECM detects a voltage below the minimum threshold on the boost control B actuator circuit while the actuator is being commanded. This low voltage condition is characteristic of a short to ground, which pulls the circuit voltage down and may cause excessive current through the output driver.

The boost control B circuit governs the second actuator in a multi-channel boost management system. A short to ground in this circuit can hold the actuator in a fixed position, eliminating the ECM's ability to modulate boost through the B channel. The engine management system will set the code, illuminate the MIL, and typically engage a reduced-power mode to protect engine components from uncontrolled boost events.

Investigation should begin with a careful inspection of the harness segments unique to the B-circuit route, since heat shields, exhaust routing, and bracket edges near the second turbocharger are common chafe points. Separating the circuit at each connector in turn while measuring resistance to ground will systematically isolate the fault location without unnecessary component replacement.

Common causes

Most-frequently reported root causes when P2C2C is logged.

  • 1
    Short to ground in the boost control B actuator signal or supply wire.
  • 2
    Chafed wiring insulation at a bracket or heat shield near the second turbocharger.
  • 3
    Moisture or debris bridging connector terminals to ground potential.
  • 4
    Internally shorted boost control B solenoid coil.
  • 5
    Connector damage allowing a terminal to contact the connector body or chassis.
  • 6
    Aftermarket accessory wiring interfering with the B-circuit.
  • 7
    ECM/PCM output driver for the B channel exhibiting an internal short.

Symptoms drivers notice

MIL illuminated, often with a limp-mode power restriction.
Loss of boost control on the B channel with fixed or default boost output.
Reduced engine performance under acceleration.
Possible overboost on the unaffected A circuit if the system compensates.
Scan tool data shows commanded versus actual boost discrepancy on the B channel.

How to diagnose P2C2C

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool and read all codes plus freeze-frame; note any companion codes.
  2. 2
    Inspect the B-circuit harness visually for chafe marks, heat damage, or connector issues.
  3. 3
    Unplug the B-circuit actuator and measure resistance from the signal wire to chassis ground; near-zero indicates a short to ground in the harness.
  4. 4
    Disconnect intermediate connectors to segment the harness and isolate the short location.
  5. 5
    Check actuator solenoid coil for internal short by measuring coil resistance.
  6. 6
    Once the external harness is confirmed clean, evaluate the ECM output driver under safe-mode testing.
  7. 7
    Repair short, replace actuator if needed, verify repair, and clear codes.

Vehicles where we've handled P2C2C

Platforms in our catalogue with confirmed P2C2C coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

What is the difference between P2C2B and P2C2C?

P2C2B is an open circuit (no current path), while P2C2C is a short to ground (unintended low-resistance ground path) on the same boost control B circuit.

Can P2C2C cause turbocharger damage?

If the fault causes a fixed high-boost condition, mechanical stress on the turbocharger and engine is possible. The ECM usually activates a safe mode, but the fault should be repaired without delay.

Should both boost control circuits be tested when P2C2C is found?

Yes. A shared wiring fault or common ground point could affect both circuits, so checking circuit A integrity at the same time is good diagnostic practice.

Does the repair require ECM reprogramming?

No. P2C2C is a hardware circuit fault. Once the wiring or actuator is repaired and codes are cleared, the ECM resumes normal boost control without reprogramming.

Disabling P2C2C in software

RaceTune can permanently disable P2C2C — 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 P2C2C 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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