P294B

Reductant Pump Performance

P294B is a generic OBD-II powertrain diagnostic trouble code: Reductant Pump Performance. 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
P294B
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P294B means

P294B is set when the engine control module (ECM) detects that the reductant (DEF/AdBlue) pump is not delivering the expected flow rate or pressure during SCR system operation. The module monitors pump feedback signals and compares actual output to commanded targets; a sustained deviation triggers this fault.

Common causes include a worn or seized pump motor, a clogged reductant filter, frozen DEF in cold climates, or electrical faults in the pump drive circuit. Air ingestion into the reductant lines after running the tank dry can also degrade pump performance and set this code.

The SCR catalyst will not receive adequate reductant injection when this fault is active, leading to elevated NOx tailpipe emissions. In markets with strict OBD regulations, continued driving with P294B active may cause the vehicle to enter a torque-limited derate after a defined number of restart cycles.

Common causes

Most-frequently reported root causes when P294B is logged.

  • 1
    Reductant pump motor worn or seized, reducing output flow.
  • 2
    Clogged reductant supply filter restricting pump inlet.
  • 3
    Frozen DEF in the tank, lines, or pump in sub-zero conditions.
  • 4
    Air lock in reductant lines after running tank empty.
  • 5
    Open or short circuit in pump motor wiring harness.
  • 6
    Failed pump control relay or fuse.
  • 7
    Low reductant tank level causing pump cavitation.

Symptoms drivers notice

MIL (check engine light) illuminated.
SCR system warning or AdBlue warning message on instrument cluster.
Increased NOx emissions detected during inspection.
Possible torque derate after multiple drive cycles with fault present.

How to diagnose P294B

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool, record all stored DTCs, and note freeze-frame data.
  2. 2
    Check DEF tank level and inspect for contaminated or frozen fluid.
  3. 3
    Inspect reductant pump fuse, relay, and wiring harness for damage or corrosion.
  4. 4
    Command the reductant pump on via bi-directional controls and measure current draw against specification.
  5. 5
    Check reductant filter condition and replace if restricted.
  6. 6
    Measure pump output pressure with a reductant pressure gauge if accessible.
  7. 7
    Replace reductant pump assembly if electrical circuit is intact but performance remains out of spec.

Vehicles where we've handled P294B

Platforms in our catalogue with confirmed P294B coverage.

BMW 530XD
2017
BMW X5
2018–2019
BMW 320D
2016
BMW 530XD 30D

Related powertrain codes

Frequently asked questions

Can I drive with P294B active?

Short-term driving is generally possible, but the SCR system will not reduce NOx effectively and a torque derate may engage after several restart cycles depending on the manufacturer's inducement strategy.

Will refilling the DEF tank clear this code?

If low level caused pump cavitation or air ingestion, refilling and priming the system may allow the code to clear after a successful drive cycle, but a hard fault in the pump itself will persist.

How do I prime the reductant pump after running the tank dry?

Most scan tools with bi-directional control can command a pump prime cycle; alternatively, refill the tank and perform several key-on cycles to allow the module to self-prime before starting the engine.

Is P294B the same as a pump circuit fault?

No. Circuit faults (open/short) typically set specific electrical codes such as P2BAD or P2BB0. P294B specifically indicates the pump is powered but not meeting its performance target.

Disabling P294B in software

RaceTune can permanently disable P294B — 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 P294B 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 EDC17C56 verified 1 software version
  • Bosch MD1CP002 verified 1 software version
  • Bosch MD1CS001 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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