P24F5

Reductant Injection Valve Control Circuit High

P24F5 is a generic OBD-II powertrain diagnostic trouble code: Reductant Injection Valve 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
P24F5
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P24F5 means

P24F5 is stored when the ECM/PCM detects that the control circuit of the DEF dosing injector valve is reading a higher-than-expected voltage. This short-to-voltage condition occurs when the control wire is inadvertently connected to a power source, typically through insulation damage, a pinched harness, or an internal fault in the ECM output driver. The module cannot pull the circuit low to command the injector, so dosing is effectively disabled.

The high circuit voltage may prevent the ECM from energising the injector coil at all, or it may cause erratic operation depending on the injector driver architecture. In either case, the SCR system loses the ability to meter DEF accurately, and NOx conversion drops significantly. The ECM logs the fault and may disable the dosing command to prevent an uncontrolled condition.

As with other reductant injector control faults, a derate strategy is typically triggered after a manufacturer-defined number of non-compliant drive cycles. Diagnosing the exact point of the voltage intrusion in the circuit is key to resolving this fault efficiently.

Common causes

Most-frequently reported root causes when P24F5 is logged.

  • 1
    Short to battery voltage or switched ignition supply on the injector control signal wire.
  • 2
    Harness routed against or pinched by a component connected to a power rail.
  • 3
    Failed ECM/PCM output driver internally shorted to a supply voltage.
  • 4
    Wiring splice near the dosing module or injector with incorrect circuit connections.
  • 5
    Damaged wiring insulation making contact with a positively charged surface.

Symptoms drivers notice

MIL and SCR/AdBlue warning lamp illuminated.
Loss of DEF dosing and reduced NOx conversion efficiency.
Torque or speed derate possible after repeated fault cycles.
Accompanying SCR efficiency or NOx sensor faults may be present.
No response from the injector during bi-directional SCR actuator test.

How to diagnose P24F5

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve and document all active and stored DTCs and any relevant freeze-frame data.
  2. 2
    Disconnect the injector connector and measure voltage on the control wire relative to chassis ground; a voltage reading with the circuit open indicates a harness short to power.
  3. 3
    Trace the control wire harness from the injector back toward the ECM, looking for pinch points or contact with fuse box wiring.
  4. 4
    Check whether the high voltage is present with the ignition off (short to battery) or only with ignition on (short to switched supply).
  5. 5
    If the harness is intact, connect a test light between the ECM control pin and ground and observe ECM commanded output; if the ECM cannot pull the circuit low, suspect an internal driver fault.
  6. 6
    Repair identified harness faults or replace the ECM as indicated.
  7. 7
    Clear codes, perform an SCR functional test, and confirm proper injector operation.

Related powertrain codes

Frequently asked questions

What is the difference between P24F4 and P24F5?

P24F4 is a circuit low (short to ground) fault, while P24F5 is a circuit high (short to voltage) fault on the same dosing injector control circuit.

Can a wiring repair fix P24F5 permanently?

Yes, if the short to voltage is in the harness. Proper insulation repair or harness replacement at the damaged section will resolve the fault.

Will an ECM replacement always fix a circuit high code?

Only if the ECM driver is confirmed faulty. Always rule out harness shorts first, as replacing the ECM without repairing a harness short will damage the new module.

Is the injector itself likely to be damaged by a circuit high fault?

Not typically. A circuit high presents excess voltage on the control line, but the injector coil itself is unlikely to be damaged unless sustained overcurrent was also present.

Disabling P24F5 in software

RaceTune can permanently disable P24F5 — 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.

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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