P27C2

EGR Cooler Bypass Control Circuit Low

P27C2 is a generic OBD-II powertrain diagnostic trouble code: EGR Cooler Bypass 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
P27C2
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P27C2 means

P27C2 is stored when the PCM detects a lower-than-expected voltage or current on the EGR cooler bypass valve control circuit. This is the complement to P27BE (circuit high) and occurs when the signal level falls below acceptable limits, typically indicating a short to ground, an open circuit in the solenoid winding, or a failed PCM driver pulling the circuit low.

The EGR cooler bypass solenoid requires a specific voltage and current level to actuate correctly. When the circuit is in a low state, the solenoid may fail to actuate, leaving the bypass valve in its spring-return default position. Depending on the valve design, this default may be either fully bypassing or fully cooling, with either condition causing suboptimal EGR thermal management.

Because this is a control circuit fault rather than a mechanical one, diagnosis focuses on the electrical path between the PCM and the actuator. A short to ground anywhere in the control wire, excessive resistance in ground return, or a failed driver output in the PCM are the primary suspects. Systematic circuit testing with basic electrical tools will identify the fault location without requiring part replacement upfront.

Common causes

Most-frequently reported root causes when P27C2 is logged.

  • 1
    Short to ground in the EGR cooler bypass solenoid control circuit wiring.
  • 2
    Open or high-resistance ground return path for the bypass solenoid.
  • 3
    EGR cooler bypass solenoid coil open circuit (broken winding).
  • 4
    Damaged or corroded connector terminal at the bypass actuator creating a high-resistance or shorted path.
  • 5
    PCM EGR bypass driver circuit fault producing insufficient output voltage.
  • 6
    Chafed control wire contacting chassis or engine ground.
  • 7
    Water intrusion into connector causing resistive short to ground.

Symptoms drivers notice

MIL illuminated.
EGR cooler bypass valve unable to actuate, defaulting to spring-return position.
Cold-start emission performance affected; extended or rough warm-up possible.
Potential companion EGR system codes if overall EGR operation is disrupted.
No significant hot-running driveability symptom in most cases.

How to diagnose P27C2

A typical diagnostic flow when this code is present.

  1. 1
    Read all DTCs and freeze frame; note any companion EGR or emissions system codes.
  2. 2
    Inspect the EGR cooler bypass actuator wiring and connector for shorts to ground or visible damage.
  3. 3
    With the connector disconnected, measure solenoid coil resistance; an open reading indicates a broken winding.
  4. 4
    Measure voltage at the solenoid connector control pin with the circuit commanded on to check for low or absent drive voltage.
  5. 5
    Check for a short to ground on the control wire by measuring resistance between the control pin and chassis ground with the PCM disconnected.
  6. 6
    Inspect and clean ground return circuit connections for the bypass actuator.
  7. 7
    Command the bypass valve via scan tool output controls and monitor current draw to distinguish a wiring fault from a solenoid or PCM fault.

Vehicles where we've handled P27C2

Platforms in our catalogue with confirmed P27C2 coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

What is the difference between P27C2 and P27BE?

P27BE is a circuit-high fault (voltage above expected range) while P27C2 is a circuit-low fault (voltage below expected range). Each points to different failure modes in the same control circuit.

If the solenoid resistance is correct, what else could cause P27C2?

A short to ground in the wiring harness or a failing PCM driver that cannot maintain adequate output voltage are the next suspects after the solenoid itself is cleared.

Does P27C2 affect hot EGR operation?

Hot EGR operation relies on the main EGR valve, not the cooler bypass valve. P27C2 primarily affects cold-start thermal management and not the core EGR recirculation function.

Can this code be caused by a recent repair or wiring work?

Yes. Incorrectly routed or pinched wiring near the EGR area after engine service is a common cause of short-to-ground conditions that set this code.

Disabling P27C2 in software

RaceTune can permanently disable P27C2 — 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 P27C2 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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