P290C

Reductant Pressure Too High

P290C is a generic OBD-II powertrain diagnostic trouble code: Reductant Pressure Too 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
P290C
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P290C means

P290C is stored when the powertrain control module determines that reductant system pressure exceeds the upper calibrated limit during SCR operation. The ECU continuously monitors the reductant pressure sensor output and expects pressure to remain within a defined operating window while the pump and dosing injector are active.

Excessive pressure can damage the dosing injector, cause reductant to be delivered at an incorrect rate, or indicate a failed pressure-relief mechanism within the supply module. The fault is confirmed after pressure remains above threshold for a calibrated time window, distinguishing it from brief spikes that occur during normal pump priming.

Diagnosis should focus on the reductant pressure regulator or return circuit first, since a blocked return path is a frequent cause. A stuck-open pump or a pressure sensor offset can also produce this code. Addressing P290C promptly prevents injector damage and ensures accurate DEF metering to the SCR catalyst.

Common causes

Most-frequently reported root causes when P290C is logged.

  • 1
    Failed or sticking reductant pressure regulator unable to bleed excess pressure.
  • 2
    Blocked reductant return line preventing pressure from relieving.
  • 3
    Faulty reductant pressure sensor with a positive offset reporting falsely high values.
  • 4
    Reductant pump control circuit fault causing the pump to run at excessive duty cycle.
  • 5
    Contamination or crystallisation in the pressure-relief valve seat holding it closed.
  • 6
    Software or calibration mismatch causing incorrect pump drive commands.

Symptoms drivers notice

MIL illuminated with P290C stored.
Possible DEF warning lamp or SCR system fault message on the dashboard.
Incorrect DEF dosing rate leading to excess or insufficient NOx reduction.
Potential reductant leakage at injector or line fittings under high pressure.
SCR efficiency monitor may log a secondary NOx-related fault.

How to diagnose P290C

A typical diagnostic flow when this code is present.

  1. 1
    Record all DTCs and freeze-frame data with a scan tool before clearing codes.
  2. 2
    Inspect reductant supply and return lines for blockages, kinks, or collapsed hoses.
  3. 3
    Monitor live reductant pressure data while commanding the pump on and off.
  4. 4
    Test the pressure-relief valve or regulator for proper operation per manufacturer procedure.
  5. 5
    Verify pressure sensor accuracy by comparing sensor reading to a calibrated reference gauge if a test port is available.
  6. 6
    Check pump control wiring and module output for over-voltage or duty-cycle error.
  7. 7
    Replace the reductant supply module if internal regulator is confirmed faulty.

Vehicles where we've handled P290C

Platforms in our catalogue with confirmed P290C coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

Is P290C more serious than P290A?

Both affect SCR function, but P290C carries a risk of physical damage to the dosing injector or lines if high pressure is sustained, making prompt diagnosis equally important.

Could a new DEF pump cause P290C?

Yes. An incorrectly specified or improperly calibrated replacement pump may produce higher pressure than the system expects, triggering this fault.

Will the engine lose power with P290C?

Not immediately, but if the SCR system is judged non-functional over multiple drive cycles, some manufacturers apply a NOx inducement strategy that limits engine output.

Can P290C and P290A be set simultaneously?

It is unusual because they represent opposite conditions, but a faulty sensor with erratic output could produce both codes. Prioritise verifying sensor accuracy in that case.

Disabling P290C in software

RaceTune can permanently disable P290C — 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 P290C 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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