P25C2

Exhaust Aftertreatment Fuel Injector Control Circuit High

P25C2 is a generic OBD-II powertrain diagnostic trouble code: Exhaust Aftertreatment Fuel Injector 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.

Code
P25C2
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P25C2 means

P25C2 is stored when the aftertreatment control module detects a high voltage or open-load condition on the exhaust aftertreatment fuel injector control circuit. The aftertreatment fuel injector (also known as a 7th injector or HC injector) sprays a small quantity of diesel fuel into the exhaust stream to create exothermic reactions in the diesel oxidation catalyst, raising exhaust temperatures for DPF regeneration.

A high-circuit condition indicates that the control signal voltage is above the expected range when the injector should be inactive or commanded to a low state. This is typically caused by a short to a voltage source in the control wiring or an open circuit on the return path. The injector itself may also have failed in a manner that presents a high-impedance or disconnected coil to the driver circuit.

Diagnosis involves checking the injector wiring harness in the high-temperature environment near the exhaust, measuring injector coil resistance, and inspecting the connector for heat damage or moisture. The control module output should be verified with a wiring diagram before replacement.

Common causes

Most-frequently reported root causes when P25C2 is logged.

  • 1
    Short to battery or ignition voltage on the injector control circuit wire.
  • 2
    Open circuit in the injector coil return (ground) path.
  • 3
    Failed aftertreatment fuel injector with an open or high-resistance coil.
  • 4
    Heat-damaged wiring harness near the exhaust causing insulation breakdown.
  • 5
    Corroded or loose connector at the aftertreatment injector.
  • 6
    Aftertreatment control module internal driver fault.
  • 7
    Fuse or relay fault in the injector supply circuit causing abnormal voltage.

Symptoms drivers notice

MIL illuminated.
DPF regeneration may be inhibited or incomplete, leading to DPF soot accumulation.
DPF warning or regeneration failure lamp may illuminate.
Possible reduced power if DPF reaches maximum soot load.
Fuel economy may be slightly affected if the engine compensates with active regeneration strategies.

How to diagnose P25C2

A typical diagnostic flow when this code is present.

  1. 1
    Scan all DTCs and check for accompanying DPF soot load or regeneration failure codes.
  2. 2
    Inspect the aftertreatment injector harness for heat damage, chafing, and connector condition.
  3. 3
    Measure aftertreatment injector coil resistance and compare to specification.
  4. 4
    With the key on (engine off), measure voltage on the control circuit at the injector connector.
  5. 5
    Trace the control wire back to the aftertreatment module and check for shorts to voltage.
  6. 6
    Command the injector using a scan tool (if supported) and observe circuit voltage response.
  7. 7
    Replace the injector or repair the harness based on test results.

Vehicles where we've handled P25C2

Platforms in our catalogue with confirmed P25C2 coverage.

BMW X5
2018–2019
BMW 530XD
2017
BMW 320D
2016
BMW 530XD 30D

Related powertrain codes

Frequently asked questions

Can DPF regeneration occur without the aftertreatment injector?

Passive regeneration from high exhaust temperatures during extended motorway driving may still occur, but active and forced regeneration will be impaired.

Is P25C2 an emissions-related code?

Yes. It relates to the aftertreatment system, which controls emissions compliance, so the MIL will be illuminated.

How urgent is this repair?

Moderately urgent. If the DPF fills beyond its cleaning threshold, more serious damage or forced limp mode may follow.

Can I perform a forced DPF regeneration with this code active?

The control module may block forced regeneration when a circuit fault is detected for safety reasons. The injector fault should be resolved first.

Disabling P25C2 in software

RaceTune can permanently disable P25C2 — 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 P25C2 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 EDC17C56 verified 1 software version
  • Bosch MD1CP002 verified 1 software version
  • Bosch MD1CS001 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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