P27C7

Turbocharger Wastegate Solenoid B Control Circuit Low

P27C7 is a generic OBD-II powertrain diagnostic trouble code: Turbocharger Wastegate Solenoid B 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
P27C7
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P27C7 means

P27C7 is the circuit-low counterpart for wastegate solenoid B on engines equipped with dual wastegate solenoid configurations or twin-turbocharger systems. The PCM monitors the electrical output circuit for solenoid B and sets this code when the measured voltage or current falls below the programmed minimum threshold, indicating a short to ground or an overloaded circuit condition.

On twin-turbo applications, solenoid A and solenoid B may control separate wastegates on each turbocharger, or they may work in sequence to stage boost delivery. A failure of solenoid B can therefore cause asymmetric boost, sequential turbo transition problems, or complete loss of boost management on the affected bank.

Diagnosis follows the same electrical approach as other solenoid low-circuit codes: verify connector integrity, measure coil resistance, check for wiring shorts to ground, and confirm PCM driver functionality. Thermal damage from proximity to exhaust components is a frequent physical cause on high-mileage turbocharged engines.

Common causes

Most-frequently reported root causes when P27C7 is logged.

  • 1
    Short to ground in the control wiring between the PCM and wastegate solenoid B.
  • 2
    Internally shorted wastegate solenoid B coil lowering circuit resistance.
  • 3
    Heat-damaged wiring insulation near the turbocharger or exhaust manifold.
  • 4
    Corroded solenoid B connector creating an unintended ground path.
  • 5
    Failed PCM output driver for the solenoid B channel.
  • 6
    Moisture or oil contamination inside the solenoid B connector.
  • 7
    Chafed wiring bundle contacting the chassis or a grounded component.

Symptoms drivers notice

MIL illuminated, potentially with reduced power mode engaged.
Noticeable boost imbalance between turbochargers on twin-turbo engines.
Poor sequential turbocharger transition or hesitation at mid-range RPM.
Overboosting or underboosting on the solenoid B controlled circuit.
Possible turbocharger noise changes under load.

How to diagnose P27C7

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool, record all DTCs and freeze-frame, and note if solenoid A codes are also present.
  2. 2
    Inspect solenoid B wiring harness for heat damage, chafing, or connector corrosion.
  3. 3
    Measure solenoid B coil resistance; an abnormally low value suggests an internal short.
  4. 4
    Perform a continuity check between the solenoid B control wire and chassis ground to detect a wiring short.
  5. 5
    Inspect the PCM connector pin for the solenoid B output for corrosion or damage.
  6. 6
    Replace solenoid B if coil resistance is out of specification and wiring is confirmed intact.
  7. 7
    Verify repair by clearing codes and performing a road test with boost monitoring via scan tool.

Vehicles where we've handled P27C7

Platforms in our catalogue with confirmed P27C7 coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

How does P27C7 differ from P27C1?

P27C1 refers to wastegate solenoid A while P27C7 refers to solenoid B. On twin-turbo or staged-boost systems, each solenoid controls a separate boost management function.

Can P27C7 cause turbocharger damage?

Yes. If solenoid B fails in a position that allows overboosting, the turbocharger and engine can be damaged. Prompt repair is important.

Is the solenoid accessible for DIY replacement?

Accessibility varies by vehicle. Many wastegate solenoids are bolt-on components near the turbocharger, but heat shields and tight packaging can make access difficult on some applications.

Should I replace both solenoids if only B is faulty?

Only the faulty solenoid needs replacement unless both show symptoms or high mileage justifies preventive replacement of the pair.

Disabling P27C7 in software

RaceTune can permanently disable P27C7 — 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 P27C7 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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