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DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P208F

P208FReductant Injection Valve Stuck Closed (Bank 2 Unit 1)

P208F indicates that the powertrain control module has commanded the reductant injection valve for bank 2 unit 1 to open, but the circuit or valve response indicates it is stuck closed. The computer detects this by monitoring the valve's electrical current or the resulting exhaust condition and seeing no expected change when activation is commanded.

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

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms.
  • A message on the dashboard indicating poor diesel exhaust fluid (DEF) quality or a reductant system fault.
  • Reduced engine power or limp mode if the vehicle's strategy derates the engine after repeated faults.
  • Increased diesel exhaust fluid consumption if the system attempts to compensate by injecting more fluid elsewhere.
  • Possible white exhaust smoke or ammonia odor if reductant is being injected incorrectly by another valve.
  • Failure to pass an emissions inspection due to the stored fault code.

Common causes, most likely first

  1. Failed reductant injection valve (bank 2 unit 1) that is mechanically stuck closed or has a burned-out solenoid.
  2. Open or shorted wiring in the valve control circuit, including chafed harnesses or corroded connectors.
  3. Blown fuse or faulty relay supplying power to the reductant injection valve.
  4. Clogged or crystallized reductant injector nozzle from urea deposits, preventing flow even when commanded.
  5. Faulty reductant pressure sensor or temperature sensor giving false feedback to the control module.
  6. Software calibration issue in the powertrain control module causing incorrect valve activation.
  7. Contaminated diesel exhaust fluid (DEF) that has degraded and caused valve sticking or blockage.

How to diagnose and fix it

  1. Inspect the reductant injection valve connector and wiring for corrosion, damage, or loose pins; clean and repair as needed.
  2. Check the fuse and relay for the reductant injection valve circuit and replace any failed components.
  3. Measure the resistance of the reductant injection valve solenoid and compare to the manufacturer's specification; replace the valve if out of range.
  4. Command the valve on with a scan tool and listen for an audible click; if no click, perform a circuit test to isolate wiring or valve failure.
  5. Remove the reductant injection valve and inspect for crystallization or blockage; clean or replace the valve if deposits are present.
  6. Verify diesel exhaust fluid quality with a refractometer and replace the fluid if contaminated or diluted.
  7. Clear the fault codes and perform a road test or forced regeneration to confirm the repair and ensure the code does not return.

Reductant valve faults that fool technicians

  • A stuck-closed reductant valve often sets no drivability symptoms because the system may default to a less efficient strategy, so the warning light is the only clue.
  • Crystallized urea deposits from a leaking or weeping injector can cause the valve to stick closed even when the electrical circuit tests perfectly.
  • The code can be set by a faulty reductant pressure sensor that reports low pressure, causing the control module to command the valve closed and then flag it as stuck.
  • On some vehicles, a weak battery or charging system issue can cause spurious reductant valve codes due to low voltage during valve actuation.
  • Replacing the valve without checking for contaminated diesel exhaust fluid often leads to repeat failures because the new valve quickly clogs with the same deposits.

Can I keep driving with P208F?

You can usually continue driving with this code, but the vehicle may enter limp mode or fail emissions testing, so schedule diagnosis soon. Avoid towing heavy loads or long trips until repaired, as reduced power may occur unexpectedly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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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