P24A6

Reductant Injector Control Circuit High Bank 1 Unit 1

P24A6 is a generic OBD-II powertrain diagnostic trouble code: Reductant Injector Control Circuit High Bank 1 Unit 1. 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
P24A6
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P24A6 means

P24A6 is set when the SCR control module detects an unexpectedly high voltage condition on the control circuit of the Bank 1 Unit 1 DEF dosing injector. The dosing injector is an electrically actuated valve that sprays a precise quantity of diesel exhaust fluid into the exhaust stream upstream of the SCR catalyst. Accurate dosing is essential for converting NOx to nitrogen and water without over-dosing, which can cause ammonia slip past the catalyst.

A high-circuit condition typically results from a short to battery voltage in the injector wiring, a failed injector solenoid with an internal winding fault, or a failing driver stage in the control module presenting high voltage on the output line when the injector should be off. The control module monitors the actual circuit state against the commanded state; a mismatch triggers the fault and the module typically disables DEF injection to protect the injector and catalyst from over-dosing.

With DEF injection disabled, the SCR catalyst cannot reduce NOx to acceptable levels. Many diesel vehicles will activate an inducement strategy after a warm-up period, progressively limiting engine power or speed until the fault is repaired. Prompt diagnosis and repair are important to avoid both the regulatory and driveability consequences of extended SCR inoperation.

Common causes

Most-frequently reported root causes when P24A6 is logged.

  • 1
    Short to battery voltage in the dosing injector wiring harness or connector.
  • 2
    Failed dosing injector solenoid with internal short or open winding.
  • 3
    Control module driver fault presenting high voltage on the injector output pin.
  • 4
    Corroded or bridged connector pins at the dosing injector due to DEF exposure.
  • 5
    Chafed wiring harness shorting to a voltage source near exhaust components.
  • 6
    Failed injector relay (if applicable) with stuck contacts energizing the circuit continuously.

Symptoms drivers notice

MIL and possible SCR or NOx warning lamp illuminated.
DEF injection disabled; increased NOx output from the tailpipe.
Engine power or speed limitation (inducement) activating after continued operation.
Possible companion NOx efficiency or catalyst efficiency codes.

How to diagnose P24A6

A typical diagnostic flow when this code is present.

  1. 1
    Record all stored DTCs and note any NOx sensor, SCR efficiency, or DEF pressure codes.
  2. 2
    Inspect the dosing injector wiring harness and connector for shorts to voltage, corrosion, or DEF damage.
  3. 3
    Measure voltage on the injector control circuit with the injector commanded off; should be near zero.
  4. 4
    Test injector solenoid resistance and compare to specification; replace the injector if out of range.
  5. 5
    Check the control module driver output voltage under commanded-off conditions before suspecting module failure.
  6. 6
    Inspect and clean the injector connector thoroughly as DEF crystallization can bridge pins.

Vehicles where we've handled P24A6

Platforms in our catalogue with confirmed P24A6 coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

Will P24A6 cause an engine derate?

Yes, on most modern diesel platforms with SCR compliance monitoring, a disabled dosing injector will trigger an inducement strategy that limits engine power or speed.

Can a high-circuit fault on P24A6 damage the SCR catalyst?

The control module typically disables injection when a circuit fault is detected, so catalyst over-dosing damage is unlikely during the fault condition; however, running without NOx reduction can still have regulatory implications.

Is the dosing injector the same as a fuel injector?

No. The DEF dosing injector sprays urea solution into the exhaust system, not fuel into the combustion chamber; it operates at lower pressure and handles a very different fluid.

Can DEF contamination cause P24A6?

Yes, DEF crystallization in the injector connector can bridge pins and create short circuits that the module detects as a high-circuit condition.

Disabling P24A6 in software

RaceTune can permanently disable P24A6 — 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 P24A6 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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