P24F2

Reductant Injection Valve Stuck Open

P24F2 is a generic OBD-II powertrain diagnostic trouble code: Reductant Injection Valve Stuck Open. 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
P24F2
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P24F2 means

P24F2 is stored when the PCM or diesel exhaust fluid (DEF) dosing control module determines that the reductant injection valve has failed in the open position. The dosing injector is a solenoid-operated valve that delivers precise metered quantities of DEF into the exhaust upstream of the SCR catalyst. A valve stuck open allows uncontrolled, continuous DEF flow into the exhaust regardless of commanded dosing.

Uncontrolled DEF injection causes ammonia slip past the SCR catalyst, potential crystallization of urea in the exhaust system, and can hydraulically foul the catalyst substrate. The dosing module typically detects a stuck-open injector by comparing commanded off-time with DEF rail pressure feedback - if pressure drops continuously when the valve should be closed, the valve is not seating properly.

This fault will illuminate the MIL and may cause the system to shut down the dosing pump to prevent further catalyst damage. Some implementations enter a reduced-power or SCR-off mode. Replacement of the dosing injector and inspection of the SCR catalyst for urea deposit blockage is typically required.

Common causes

Most-frequently reported root causes when P24F2 is logged.

  • 1
    Mechanical failure of the dosing injector needle seat allowing continuous flow.
  • 2
    Foreign material or DEF crystallization preventing the injector needle from closing.
  • 3
    Electrical fault holding the solenoid energized continuously.
  • 4
    Worn or damaged injector sealing surfaces from thermal cycling.
  • 5
    Contaminated DEF solution causing deposit buildup inside the injector.
  • 6
    Faulty dosing control module output driver holding the valve open.
  • 7
    Low DEF quality or incorrect fluid type causing accelerated injector wear.

Symptoms drivers notice

MIL illuminated.
White or grey exhaust smoke with ammonia odor, especially at idle.
Visible urea crystallization deposits in the exhaust tail pipe.
DEF consumption significantly higher than normal.
Possible SCR catalyst blockage or efficiency reduction over time.

How to diagnose P24F2

A typical diagnostic flow when this code is present.

  1. 1
    Record all DTCs and freeze frame data; note any DEF pressure or flow codes.
  2. 2
    Inspect the exhaust outlet for urea deposits indicating continuous injection.
  3. 3
    Check DEF rail pressure drop behavior with the injector commanded off using a scan tool.
  4. 4
    Inspect the dosing injector electrical connector and wiring for a short that could hold the solenoid open.
  5. 5
    Remove and inspect the injector for debris, crystallization, or damaged sealing surfaces.
  6. 6
    Replace the dosing injector if found to be mechanically stuck or damaged.
  7. 7
    After replacement, inspect the SCR catalyst inlet for urea blockage and flush if necessary.

Vehicles where we've handled P24F2

Platforms in our catalogue with confirmed P24F2 coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

Is it safe to drive with P24F2 active?

Extended driving is not recommended. Continuous DEF injection can damage the SCR catalyst through ammonia slip and urea crystallization, turning a relatively inexpensive injector repair into a costly catalyst replacement.

Can DEF quality cause a stuck injector?

Yes. Low-quality or contaminated DEF with excessive urea concentration or impurities can leave crystalline deposits inside the injector body that prevent the needle from seating.

Will the system shut off DEF dosing automatically when P24F2 is set?

Many systems will command the dosing pump off when a stuck-open injector is confirmed to prevent further catalyst damage, but this behavior varies by manufacturer and calibration.

Does the SCR catalyst need to be replaced if P24F2 was active for a long time?

Possibly. Prolonged ammonia slip and urea crystallization can block the catalyst substrate. After injector replacement, monitor post-catalyst NOx sensor readings and SCR efficiency to determine if catalyst replacement is also needed.

Disabling P24F2 in software

RaceTune can permanently disable P24F2 — 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 P24F2 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 EDC17CP09 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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