P27C1

Turbocharger Wastegate Solenoid A Control Circuit Low

P27C1 is a generic OBD-II powertrain diagnostic trouble code: Turbocharger Wastegate Solenoid A Control 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
P27C1
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P27C1 means

P27C1 is stored when the PCM detects a lower-than-expected voltage or current on the control circuit for turbocharger wastegate solenoid A. The wastegate solenoid regulates boost pressure by controlling the pneumatic or electronic signal that opens or closes the wastegate valve, allowing exhaust gas to bypass the turbine wheel.

A low circuit condition generally points to a short to ground somewhere in the solenoid control wiring, an internally shorted solenoid coil, or a failed PCM output driver. Less commonly, a poor ground reference at the solenoid or PCM can mimic this condition. The fault is typically detected during the PCM's continuous electrical circuit monitoring.

With an inoperative wastegate solenoid, boost pressure may be uncontrolled, leading to overboosting and potential engine damage, or the wastegate may default open and the engine may run with very little boost. Either condition warrants immediate diagnosis to prevent secondary damage to the turbocharger or engine.

Common causes

Most-frequently reported root causes when P27C1 is logged.

  • 1
    Short to ground in the wiring harness between the PCM and wastegate solenoid A.
  • 2
    Internally shorted wastegate solenoid A coil reducing circuit resistance below threshold.
  • 3
    Corroded or damaged connector pins at the solenoid or PCM causing unintended ground path.
  • 4
    Failed PCM output driver for the wastegate solenoid A circuit.
  • 5
    Chafed wiring contacting the vehicle chassis or exhaust components.
  • 6
    Moisture ingress into the solenoid connector creating a ground fault.

Symptoms drivers notice

MIL on with possible boost pressure outside normal operating range.
Engine may overboost or underboost depending on wastegate default position.
Reduced engine performance or activation of limp-home power restriction.
Possible audible boost leak or hissing if overboosting opens relief valves.
Intermittent loss of power correlated with solenoid circuit instability.

How to diagnose P27C1

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all DTCs and freeze-frame data with a scan tool before clearing codes.
  2. 2
    Inspect the wastegate solenoid A connector and wiring for signs of chafing, heat damage, or corrosion.
  3. 3
    Measure resistance of the wastegate solenoid A coil and compare to specification; a very low reading indicates an internal short.
  4. 4
    Check for continuity between the solenoid control wire and chassis ground to identify a wiring short to ground.
  5. 5
    Verify PCM ground and power supply circuits are within specification.
  6. 6
    Substitute a known-good solenoid if wiring checks pass, to rule out an internal solenoid fault.
  7. 7
    If solenoid and wiring are confirmed good, inspect the PCM driver circuit for damage.

Vehicles where we've handled P27C1

Platforms in our catalogue with confirmed P27C1 coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

What does 'circuit low' mean for P27C1?

Circuit low means the PCM measured a voltage or current on the solenoid control wire that is below the expected operating range, most often caused by a short to ground.

Can a bad solenoid trigger P27C1?

Yes. An internally shorted solenoid coil lowers circuit resistance and pulls the control voltage below the PCM threshold, setting P27C1.

Is P27C1 dangerous to ignore?

Yes. An inoperative wastegate solenoid can cause persistent overboosting or no boost at all, either of which can lead to engine damage if ignored.

Does P27C1 always mean the solenoid needs replacement?

Not always. A wiring short to ground can produce the same code. Always diagnose the circuit fully before replacing the solenoid.

Disabling P27C1 in software

RaceTune can permanently disable P27C1 — 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 P27C1 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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