P25B2
Reductant Pump Control Module PerformanceP25B2 is a generic OBD-II powertrain diagnostic trouble code: Reductant Pump Control Module 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.
What P25B2 means
P25B2 is stored when the ECM detects that the reductant pump control module is not performing within expected parameters. This is a rationality or performance fault rather than a simple circuit fault; the module may be receiving correct commands but is returning implausible feedback signals, is failing to achieve commanded pump speeds, or is reporting internal diagnostic trouble to the ECM via a controller area network message or a dedicated feedback line.
The dosing control module manages pump speed, heater control, and quality sensor reading in an integrated manner on many platforms. A performance fault can arise from module internal hardware degradation, communication errors on the CAN bus between the module and ECM, module supply voltage out of range, or persistent mechanical load on the pump (from blocked filters or frozen DEF) that the module cannot compensate for and flags as an error.
Technicians should verify module power supply and ground quality, inspect CAN bus wiring to the module for damage or termination faults, and use a scan tool to review module-reported data including pump current, fluid temperature, and quality readings. If all external inputs are correct but the module continues to report performance faults, the dosing module assembly is the likely failed component.
Common causes
Most-frequently reported root causes when P25B2 is logged.
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1
Internal hardware failure within the reductant dosing control module.
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2
Unstable or low supply voltage to the dosing module.
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3
Poor module ground causing reference offset errors.
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4
CAN bus communication fault between the dosing module and ECM.
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5
Blocked DEF filter or strainer causing pump overload.
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6
Frozen DEF imposing excessive mechanical resistance on the pump.
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7
Repeated pump stalls damaging the module drive circuitry.
Symptoms drivers notice
How to diagnose P25B2
A typical diagnostic flow when this code is present.
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1
Record all stored codes and module-reported live data values with a scan tool.
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2
Check supply voltage and ground at the dosing module connector under load.
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3
Inspect CAN bus wiring to the dosing module for damage, corrosion, or broken termination resistors.
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4
Command the pump via scan tool and observe reported pump speed and current feedback.
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5
Inspect and replace the DEF filter or strainer if flow restriction is suspected.
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6
Perform a system purge and reinitialize the dosing module if the vehicle calibration supports it.
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7
Replace the dosing control module if all external circuits are verified within specification.
Vehicles where we've handled P25B2
Platforms in our catalogue with confirmed P25B2 coverage.
Related powertrain codes
Frequently asked questions
Is P25B2 always a module replacement job?
Not always. Supply voltage issues, blocked filters, or CAN bus faults can cause performance failures that are resolved without replacing the module.
Can frozen DEF damage the pump module?
Yes. Ice in the lines or pump chamber can seize the pump and overload the drive circuitry inside the module, causing permanent damage.
How do I know if the CAN bus is the problem?
Check CAN bus termination resistance between the two bus wires; 60 ohms indicates correct dual termination. Also scan for CAN-related codes or module communication loss codes alongside P25B2.
Is the dosing module and pump one assembly or separate?
This varies significantly by platform. On many systems they are integrated into one replaceable unit mounted to or inside the DEF tank.
Disabling P25B2 in software
RaceTune can permanently disable P25B2 — 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.
ECUs with a P25B2 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.
Got P25B2 in your scan?
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