P27C9

Turbocharger Wastegate Solenoid B Control Circuit High

P27C9 is a generic OBD-II powertrain diagnostic trouble code: Turbocharger Wastegate Solenoid B Control Circuit High. 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
P27C9
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P27C9 means

P27C9 is set when the PCM detects a higher-than-expected voltage on the control circuit for wastegate solenoid B. A circuit-high condition on a solenoid driver typically results from an open circuit in the control wiring, a failed solenoid with an open coil, or an unintended connection to a voltage source that pulls the circuit high when the PCM commands the output low.

With an open control circuit, the PCM cannot energise solenoid B, so the wastegate defaults to its mechanical rest position. Depending on the system design, this may mean the wastegate stays fully open (limiting boost) or fully closed (risking overboost). Either state removes active boost regulation from that solenoid channel.

Diagnosis involves careful voltage and continuity testing of the entire solenoid B circuit. Technicians should check for broken wires, pulled connector terminals, and opens within the solenoid coil itself. The PCM output driver should only be suspected after the external circuit is fully verified as intact.

Common causes

Most-frequently reported root causes when P27C9 is logged.

  • 1
    Open circuit in the wiring harness between the PCM and wastegate solenoid B.
  • 2
    Open (broken) coil inside wastegate solenoid B.
  • 3
    Pulled or backed-out terminal in the solenoid B connector.
  • 4
    Short to battery voltage on the solenoid B control wire.
  • 5
    Failed PCM output driver presenting an unintended high signal.
  • 6
    Corroded connector creating high-resistance or intermittent open circuit.
  • 7
    Wiring damage from road debris or heat causing a broken conductor.

Symptoms drivers notice

MIL on, potentially accompanied by a reduced power warning.
Fixed or unresponsive boost level due to solenoid B being permanently de-energised.
Sluggish acceleration if the wastegate defaults open and boost is limited.
Possible overboost condition if the wastegate defaults closed on a pressure-referenced system.
No change in boost when solenoid B is commanded by the scan tool during actuator tests.

How to diagnose P27C9

A typical diagnostic flow when this code is present.

  1. 1
    Read and record all DTCs; check for companion codes related to boost pressure or other solenoids.
  2. 2
    Perform a scan tool actuator test for wastegate solenoid B and listen for a click indicating solenoid energisation.
  3. 3
    Disconnect the solenoid B connector and measure coil resistance; an open reading (infinite resistance) indicates a failed solenoid.
  4. 4
    Check for battery voltage on the control wire at the solenoid connector with the ignition on and PCM commanding the circuit low.
  5. 5
    Inspect the entire harness run for breaks, open splices, or loose terminals.
  6. 6
    Verify PCM connector integrity for the solenoid B driver pin.
  7. 7
    Replace solenoid B if coil is open, or repair wiring fault as found.

Vehicles where we've handled P27C9

Platforms in our catalogue with confirmed P27C9 coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

What is the difference between P27C9 and P27C7?

P27C7 is a circuit-low fault (short to ground or overcurrent), while P27C9 is a circuit-high fault (open circuit or short to voltage) on the same solenoid B channel.

Does an open solenoid coil always set P27C9?

Yes. When the PCM commands the circuit low but the coil is open, the control wire floats high, which the PCM interprets as a circuit-high fault.

Can I test the solenoid with a multimeter?

Yes. With the connector unplugged, measure resistance across the solenoid terminals. An open reading (OL or infinite) confirms the coil is broken.

Will P27C9 cause a no-start condition?

No, the engine will typically start and run, but boost management on that channel will be compromised, resulting in performance issues rather than a no-start.

Disabling P27C9 in software

RaceTune can permanently disable P27C9 — 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 P27C9 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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