P246B

Exhaust Gas Recirculation Cooler Bypass Control Valve Stuck Closed

P246B is a generic OBD-II powertrain diagnostic trouble code: Exhaust Gas Recirculation Cooler Bypass Control Valve Stuck Closed. 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
P246B
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P246B means

P246B is set when the ECM determines that the EGR cooler bypass control valve is stuck in the closed position and cannot be commanded open. With the valve stuck closed, exhaust gas is permanently routed through the EGR cooler even during cold-start conditions where the ECM would normally command the bypass open to deliver warm EGR to the intake.

A bypass valve stuck closed generally has a less severe immediate impact than a stuck-open condition because cooled EGR is the normal operating mode; however, it prevents the intended cold-start warm-up strategy, can slow catalyst light-off, and will trigger the MIL due to inability to control the valve as commanded.

The diagnostic process is similar to P245B: use the scan tool actuator test to verify the valve response, check the actuator electrically, and inspect for mechanical binding. On some designs the bypass valve is vacuum-operated; a broken vacuum line or failed solenoid would prevent the valve from opening. Carbon deposits can also hold the valve closed on diesel applications.

Common causes

Most-frequently reported root causes when P246B is logged.

  • 1
    Carbon deposits or mechanical seizure holding the bypass valve in the closed position.
  • 2
    Failed actuator unable to generate sufficient force to open the valve.
  • 3
    Broken, kinked, or disconnected vacuum line on vacuum-actuated designs.
  • 4
    Failed vacuum switching solenoid not supplying vacuum to the actuator.
  • 5
    Open circuit or wiring fault preventing actuator energisation.
  • 6
    Faulty position sensor reporting closed when open.
  • 7
    Faulty ECM output driver or control logic.

Symptoms drivers notice

MIL illuminated.
Slightly slower cold-start warm-up or catalyst light-off.
EGR-related cold-start emissions higher than expected.
No major driveability concerns at normal operating temperature.

How to diagnose P246B

A typical diagnostic flow when this code is present.

  1. 1
    Read all DTCs and freeze-frame data with a scan tool.
  2. 2
    Use the scan tool to command the bypass valve open and monitor any position feedback or actuator response.
  3. 3
    Inspect the bypass valve actuator for vacuum lines (if applicable) and electrical connections.
  4. 4
    Check vacuum supply to the actuator during an open command on vacuum-operated systems.
  5. 5
    Measure actuator electrical supply and signal with the valve commanded open.
  6. 6
    Remove and inspect the bypass valve for carbon binding or physical damage.
  7. 7
    Replace the actuator, solenoid, or valve assembly as indicated by test results.

Vehicles where we've handled P246B

Platforms in our catalogue with confirmed P246B coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

Is P246B more or less serious than P245B?

Generally less immediately serious because cooled EGR is the default operating mode, but it still triggers MIL and disables part of the EGR cold-start strategy.

Can a failed vacuum solenoid cause P246B?

Yes. On vacuum-actuated bypass valves, a failed switching solenoid that cannot supply vacuum will prevent the valve from opening and set this code.

Will the engine run normally with P246B?

In most cases yes, especially at normal operating temperatures; cold-start behaviour may be marginally affected but power and economy are usually not impacted.

Do I need to clean or replace the EGR cooler as well?

Only if there is evidence of cooler blockage or damage; P246B relates to the bypass valve, not the cooler core itself.

Disabling P246B in software

RaceTune can permanently disable P246B — 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 P246B 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
  • Bosch EDC17C60 verified 1 software version
  • Bosch EDC17CP09 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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