P2B72
Reductant Pump Control Circuit HighP2B72 is a generic OBD-II powertrain diagnostic trouble code: Reductant Pump Control Circuit 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.
What P2B72 means
P2B72 is set when the control module detects that the voltage on the reductant (DEF/AdBlue) pump control circuit is higher than expected. The pump is typically driven by a pulse-width modulated (PWM) ground-side driver inside the SCR dosing module. When the feedback voltage on that control line is high and does not respond to commanded duty-cycle changes, the module flags a circuit high fault.
This fault directly disables the ability of the SCR system to inject the correct amount of diesel exhaust fluid into the exhaust stream. Without proper reductant delivery, NOx conversion efficiency drops, tailpipe emissions rise, and the vehicle may enter a derate or inducement strategy depending on regulatory requirements for that market and model year.
Diagnosis should confirm whether the pump itself is receiving correct supply voltage and ground before condemning the dosing control unit. A high-resistance open on the ground driver path, a broken ground wire in the harness, or an internal failure of the dosing module output stage are the most frequent causes. Always verify harness integrity and connector seating at both the pump and the dosing module before replacing components.
Common causes
Most-frequently reported root causes when P2B72 is logged.
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1
Open circuit or high resistance in the pump ground control wire.
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2
Failed low-side driver inside the SCR dosing control module.
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3
Short to battery voltage on the pump control signal wire.
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4
Corroded or poorly seated connector at the reductant pump or dosing module.
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5
Damaged pump harness caused by heat, vibration, or abrasion.
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6
Reductant pump internal winding short creating abnormal back-EMF on the control circuit.
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7
Fuse or relay supplying the dosing system open-circuited, causing floating voltage on the control line.
Symptoms drivers notice
How to diagnose P2B72
A typical diagnostic flow when this code is present.
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1
Connect a scan tool to retrieve all DTCs and command the reductant pump on to observe control circuit response.
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2
Measure battery supply voltage at the pump connector to confirm the pump is receiving power.
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3
Check the pump ground control wire voltage while the module commands pump operation; expect a low voltage when active.
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4
Inspect the harness between the pump and dosing module for shorts to voltage, open circuits, or damaged insulation.
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5
Verify connector integrity at both the pump and the SCR dosing module.
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6
Test the pump independently by applying appropriate supply voltage and ground if harness checks out.
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7
Replace or repair the dosing control module if the internal driver is confirmed faulty after all external checks pass.
Vehicles where we've handled P2B72
Platforms in our catalogue with confirmed P2B72 coverage.
Related powertrain codes
Frequently asked questions
Can frozen DEF cause P2B72?
Frozen DEF can seize the pump mechanically, which may overload the driver circuit and cause a high-side fault, but P2B72 is primarily an electrical control circuit fault rather than a fluid issue.
What is the difference between a control circuit high and a control circuit low fault?
A high fault means the voltage on the control wire is above the expected range, typically indicating an open ground path or a short to voltage. A low fault means voltage is below range, usually indicating a short to ground.
Will the vehicle go into limp mode with P2B72?
Depending on the calibration and regional emissions regulations, prolonged loss of reductant dosing can trigger a speed or power derate strategy.
Is the reductant pump part of the dosing module assembly?
On many platforms the pump, heater, and level sensor are integrated into a single DEF tank module, while the dosing injector and control electronics are separate. Check the vehicle-specific service information.
Disabling P2B72 in software
RaceTune can permanently disable P2B72 — 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 P2B72 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.
Got P2B72 in your scan?
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