P242E

Reductant Pressure Too High

P242E is a generic OBD-II powertrain diagnostic trouble code: Reductant Pressure Too 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.

Code
P242E
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
Need P242E disabled?
RaceTune permanently disables any OBD-II trouble code on supported ECUs — for motorsport, off-road, and export use.
→

What P242E means

P242E is set when the aftertreatment control module detects that the diesel exhaust fluid (DEF) delivery pressure is above the acceptable maximum threshold. The SCR dosing system uses a pump to pressurize DEF from the tank to the dosing injector. The system is engineered to operate within a defined pressure window; exceeding the upper limit can damage the injector, cause seals to fail, or result in over-dosing of reductant into the exhaust, which can deposit solid urea crystals in the exhaust pipe or SCR catalyst.

Common causes include a stuck-open pressure relief valve, a failed dosing pump delivering unregulated high pressure, or a blocked dosing injector causing back-pressure to build in the supply line. The control module reads pressure from a dedicated sensor in the DEF supply line and compares it against the commanded pressure map.

Because this fault can lead to physical damage of the dosing injector or catalyst, it should be addressed without delay. Continued operation with over-pressure can cause urea crystallization in the dosing injector tip, eventually requiring expensive catalyst cleaning or replacement. Many platforms will limit SCR operation or trigger an engine inducement upon persistent detection.

Common causes

Most-frequently reported root causes when P242E is logged.

  • 1
    Stuck or failed DEF pressure relief valve not limiting maximum pressure.
  • 2
    Faulty DEF dosing pump delivering pressure beyond its regulated output.
  • 3
    Blocked or partially clogged DEF dosing injector causing pressure buildup.
  • 4
    Failed DEF pressure sensor providing an inaccurately high reading.
  • 5
    Wiring fault causing the pump to run at maximum duty cycle regardless of command.
  • 6
    Air trapped in the DEF supply line causing erratic pressure spikes.

Symptoms drivers notice

MIL or amber SCR warning lamp illuminated.
Possible over-dosing of DEF causing white exhaust smoke or ammonia smell.
SCR efficiency codes may appear concurrently if catalyst is affected.
Potential engine power limitation depending on platform inducement strategy.

How to diagnose P242E

A typical diagnostic flow when this code is present.

  1. 1
    Record all DTCs and freeze-frame data; note any companion SCR or dosing injector codes.
  2. 2
    Use live data to observe DEF system pressure during pump-on and pump-off phases.
  3. 3
    Inspect the DEF pressure relief valve for proper operation and replace if stuck open is confirmed.
  4. 4
    Check the DEF dosing pump output pressure against specification with a calibrated pressure gauge if accessible.
  5. 5
    Test the DEF pressure sensor by comparing its reading to the gauge; replace if readings diverge.
  6. 6
    Inspect the dosing injector for blockage or crystallized deposits that could cause back-pressure.
  7. 7
    Check pump control wiring for shorts to voltage that could cause the pump to over-deliver.

Vehicles where we've handled P242E

Platforms in our catalogue with confirmed P242E coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

Can P242E damage the SCR catalyst?

Yes, persistent over-pressure leading to over-dosing can deposit solid urea in the catalyst substrate, degrading its efficiency and potentially requiring cleaning or replacement.

Is P242E the same as P242F (pressure too low)?

No. P242E is specifically for pressure above the upper threshold, while P242F covers pressure below the lower threshold; the root causes and repairs differ significantly.

Can a frozen DEF line cause P242E?

A partially thawed line with trapped ice could cause a transient pressure spike, but persistent P242E is more typically caused by a mechanical or electrical pump or valve fault.

How urgent is it to repair P242E?

It should be repaired promptly because over-pressure can physically damage the dosing injector and catalyst; continued operation risks expensive downstream repairs.

Disabling P242E in software

RaceTune can permanently disable P242E — 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 P242E 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.

Got P242E in your scan?

Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.

Upload your file