P24A8
Reductant Injector Control Circuit Open Bank 1 Unit 1P24A8 is a generic OBD-II powertrain diagnostic trouble code: Reductant Injector Control Circuit Open 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.
What P24A8 means
P24A8 is stored when the SCR control module detects an open circuit condition in the Bank 1 Unit 1 DEF dosing injector control circuit. An open circuit means current cannot flow through the injector solenoid when the module commands it on, resulting in complete loss of DEF dosing capability. Without DEF injection the SCR catalyst cannot catalyze the reduction of NOx, and exhaust NOx levels rise above regulatory limits.
The most common causes of an open circuit are a broken or corroded wire in the harness between the control module and the injector, a failed injector solenoid with an internally open coil winding, or a disconnected or severely corroded connector. Because the dosing injector operates in proximity to the hot exhaust system and is exposed to DEF mist, heat cycling and chemical exposure make this circuit particularly vulnerable to degradation over time.
As with other SCR injector circuit faults, the control module will disable DEF injection when an open circuit is confirmed. On vehicles subject to emissions compliance inducement, this will lead to progressive engine power limitation the longer the fault remains unrepaired. Diagnosis is straightforward and should begin with a visual inspection followed by continuity testing of the injector wiring before the injector itself is replaced.
Common causes
Most-frequently reported root causes when P24A8 is logged.
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1
Broken or corroded wire in the dosing injector harness creating an open circuit.
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2
Failed dosing injector solenoid with an internally open coil winding.
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3
Disconnected injector connector or severely corroded pins preventing electrical contact.
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4
Blown fuse in the injector supply circuit removing power to the dosing circuit.
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5
Control module output pin damage preventing the drive signal from reaching the injector.
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6
Heat-damaged wiring near the exhaust system causing conductor fracture.
Symptoms drivers notice
How to diagnose P24A8
A typical diagnostic flow when this code is present.
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1
Retrieve all stored DTCs and freeze-frame data including any NOx or SCR efficiency codes.
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2
Visually inspect the dosing injector wiring harness for breaks, melted insulation near exhaust, or disconnected connectors.
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3
Check continuity of the injector control circuit from the module connector pin to the injector connector pin.
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4
Measure injector solenoid resistance at the injector connector; an open reading confirms a failed solenoid.
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5
Inspect fuses in the injector supply circuit and replace any that are blown.
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6
If wiring and fuses pass, test the control module output pin for a proper drive signal before replacing the module.
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7
After repairs, clear codes and verify SCR system operation with a scan tool by monitoring DEF dosing duty cycle.
Vehicles where we've handled P24A8
Platforms in our catalogue with confirmed P24A8 coverage.
Related powertrain codes
- P2400 — Evaporative Emission System Leak Detection Pump Control Circuit/Open
- P2401 — Evaporative Emission System Leak Detection Pump Control Circuit Low
- P2402 — Evaporative Emission System Leak Detection Pump Control Circuit High
- P2404 — EVAP Leak Detection Pump Sense Circuit: Implausible Signal
- P2405 — Evaporative Emission System Leak Detection Pump Sense Circuit Low
- P2407 — Evaporative Emission System Leak Detection Pump Sense Circuit Intermittent/Erratic
Frequently asked questions
How is P24A8 different from P24A6?
P24A8 is an open-circuit fault meaning no current can flow, while P24A6 is a high-circuit fault typically caused by a short to voltage; the root causes and wiring checks differ accordingly.
Can a loose connector cause P24A8?
Yes, a partially disconnected or corroded connector at the dosing injector is a common cause of open-circuit faults and should be the first physical check.
Will the engine derate immediately when P24A8 sets?
Most platforms allow a brief grace period before inducement activates; the exact timing depends on the manufacturer's compliance calibration.
Is it safe to drive with P24A8 active?
The vehicle may operate normally initially, but continued driving with inactive DEF injection violates emissions regulations and will eventually trigger power limitation; repair should be a priority.
Disabling P24A8 in software
RaceTune can permanently disable P24A8 — 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.
ECUs with a P24A8 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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