P24C2
Reductant Pressure Too LowP24C2 is a generic OBD-II powertrain diagnostic trouble code: Reductant Pressure Too Low. 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 P24C2 means
P24C2 is stored when the ECM detects that the pressure in the DEF (AdBlue) supply system is below the minimum threshold required for proper dosing. The SCR dosing system relies on a pump to pressurize the DEF supply line to the dosing module. Insufficient pressure prevents accurate metering of reductant into the exhaust stream, reducing NOx conversion efficiency.
This code commonly results from a failed DEF supply pump, a blocked or kinked supply line, an empty or near-empty DEF tank, or a leaking pressure line. In some systems, a stuck-open pressure relief valve can also bleed down line pressure below the threshold. The ECM monitors pressure via a dedicated sensor in the supply circuit and logs this fault when pressure remains below threshold for a calibrated duration.
When P24C2 is active, the SCR system may reduce or suspend DEF dosing, causing NOx emissions to exceed regulatory limits. Depending on calibration and jurisdiction, the vehicle may enter a torque derate after a defined period of non-compliance. Diagnosis should start with DEF level, pump operation, and pressure sensor signal verification before component replacement.
Common causes
Most-frequently reported root causes when P24C2 is logged.
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1
Empty or critically low DEF tank.
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2
Failed DEF supply pump not generating adequate pressure.
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3
Blocked or kinked DEF supply line restricting flow.
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4
Leaking DEF pressure line or fitting causing pressure loss.
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5
Stuck-open pressure relief valve bleeding system pressure.
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6
Faulty DEF pressure sensor providing incorrect low reading.
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7
DEF filter clogged with urea crystals restricting flow to the pump.
Symptoms drivers notice
How to diagnose P24C2
A typical diagnostic flow when this code is present.
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1
Check DEF tank level first; refill if low before further diagnosis.
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2
Connect a scan tool and review live DEF pressure sensor data during pump operation.
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3
Command the DEF pump on with the scan tool and listen for pump operation.
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4
Inspect DEF supply lines and connections for kinks, leaks, or crystallization blockage.
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5
Inspect the DEF filter element and replace if clogged.
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6
Measure DEF pump supply voltage and ground to rule out electrical supply issues.
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7
Replace the DEF pressure sensor if live data reads low but physical pressure checks are normal.
Vehicles where we've handled P24C2
Platforms in our catalogue with confirmed P24C2 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
Will P24C2 go away after filling the DEF tank?
If low DEF level was the sole cause, the fault may clear after refilling and completing a drive cycle. However, if the pump or lines are at fault, the code will persist regardless of DEF level.
How quickly will the vehicle derate with P24C2?
Derate timing varies by manufacturer calibration and regulatory region. Most systems allow a grace period of hours or miles before initiating a torque reduction.
Can I drive with P24C2 active?
Short-term driving is generally possible, but the underlying cause must be repaired to prevent progressive derate and to maintain emissions compliance.
Is P24C2 the same as P204B?
They are related but distinct. P204B is a broad reductant pressure performance code, while P24C2 specifically indicates pressure is confirmed too low, suggesting a supply or delivery failure rather than a general performance deviation.
Disabling P24C2 in software
RaceTune can permanently disable P24C2 — 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 P24C2 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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