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DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P208B

P208BReductant Pump A Control Performance/Stuck Off

P208B indicates that the engine control module has commanded the reductant pump to run but has not detected the expected pressure or current feedback, so it flags the pump circuit as stuck off. The module monitors the pump's electrical load and the resulting pressure in the diesel exhaust fluid system, and when either stays flat during a commanded prime or dosing event, this code sets.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

  • Illumination of the malfunction indicator lamp, often with no other noticeable symptoms.
  • A pending or active reduction in engine power or torque as the module limits dosing to protect the aftertreatment system.
  • Driver information messages warning of low diesel exhaust fluid pressure or an emissions system fault.
  • Rough running or hesitation under load if the module enters a derate strategy.
  • Failure to complete a diesel exhaust fluid dosing cycle during a scan-tool actuation test.
  • No change in vehicle behavior when the pump is commanded on with a bidirectional scan tool.

Common causes, most likely first

  1. A failed reductant pump motor or internal pump controller that no longer rotates when commanded.
  2. An open circuit in the pump power feed or ground circuit, including a blown fuse or corroded connector terminal.
  3. A short to ground or short to voltage on the pump control wire that prevents the module from driving the pump.
  4. A restricted or frozen diesel exhaust fluid pickup, filter, or supply line that prevents the pump from building pressure.
  5. A faulty reductant pressure sensor that reports no pressure even though the pump is running.
  6. A software or calibration issue in the engine control module that misinterprets pump feedback.
  7. A seized or contaminated pump caused by crystallized diesel exhaust fluid from prolonged storage or incorrect fluid.

How to diagnose and fix it

  1. Connect a scan tool and command the reductant pump on while watching pump current and pressure feedback to confirm the fault is present.
  2. Inspect the pump fuse, relay, and harness connectors for corrosion, loose terminals, or chafed wiring before condemning any component.
  3. Measure voltage and ground at the pump connector during a commanded prime to verify power and ground are present.
  4. Check the diesel exhaust fluid level, condition, and filter, and verify the pickup and supply line are not restricted or frozen.
  5. Compare the pressure sensor reading with a known-good mechanical gauge or a scan-tool pressure test to rule out a false low-pressure report.
  6. If electrical and hydraulic checks pass, substitute a known-good pump or perform a pump actuation test with a bidirectional tool to confirm pump operation.
  7. After repair, clear the code and run a diesel exhaust fluid system test or a drive cycle to verify the monitor completes without resetting.

What the pump command really reveals

  • A pump that runs but produces no pressure often points to a restricted pickup or crystallized fluid rather than a failed motor, so check the fluid condition before replacing the pump.
  • The code can set from a pressure sensor that reads low even when the pump is working, which is a common misdiagnosis trap that leads to unnecessary pump replacement.
  • In cold climates, frozen diesel exhaust fluid in the tank or lines can mimic a stuck-off pump and set this code without any electrical fault.
  • A weak or failing battery can cause the module to abort the pump prime and log this code, so verify system voltage during actuation tests.
  • Aftermarket or contaminated diesel exhaust fluid can leave deposits that seize the pump over time, and this code may be the first warning of a fluid quality problem.

Can I keep driving with P208B?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy loads and long trips because the module may derate power and the aftertreatment system can be damaged by continued operation without dosing. If the warning lamp flashes or a power reduction message appears, stop driving and arrange service.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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