P2C30
Reductant Tank Level Sensor Circuit - HighP2C30 is a generic OBD-II powertrain diagnostic trouble code: Reductant Tank Level Sensor 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.
What P2C30 means
P2C30 is logged when the ECM detects a higher-than-expected voltage on the signal circuit of the reductant tank level sensor. The level sensor typically operates on a variable-resistance or variable-voltage principle similar to a fuel level sender; the ECM expects the signal to vary within a calibrated voltage window proportional to fluid depth in the tank. A signal that pins at or above the maximum expected voltage indicates a short to reference voltage, a broken float stuck at the full-tank position, or an open in the low-reference (ground) path that causes the signal to float high.
Because the reductant tank level sensor is submerged in DEF, urea crystallisation on sensor contacts and float arm corrosion are common physical failure modes in addition to conventional wiring faults. Cold climates accelerate crystal buildup, and sensors that are seldom exercised can seize in a fixed position.
An inaccurate level signal prevents the driver information system from correctly warning about low DEF, which can lead to the tank running dry unexpectedly and SCR dosing stopping entirely. It also interferes with the ECM calculation of anticipated range before a derate event, making fleet management and compliance planning unreliable.
Common causes
Most-frequently reported root causes when P2C30 is logged.
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1
Short to the sensor reference or supply voltage in the level sensor signal wiring.
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2
Open ground (low reference) circuit causing the signal to float to the supply rail.
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3
Float arm seized in the full-tank position due to DEF crystallisation or corrosion.
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4
Corroded or contaminated level sensor connector terminals.
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5
Failed level sensor sender element with an internal open circuit.
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6
Damaged harness insulation creating a short to an adjacent voltage source.
Symptoms drivers notice
How to diagnose P2C30
A typical diagnostic flow when this code is present.
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1
Record all DTCs and freeze-frame data with a scan tool.
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2
Access the reductant tank level sensor connector; with the connector unplugged, measure voltage on the signal wire to confirm it is at or near supply voltage (indicating a short to power or open ground).
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3
Inspect the connector and harness for corrosion, DEF crystal contamination, or damaged insulation.
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4
Check the low-reference ground path continuity from the sensor connector back to the ECM ground.
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5
If wiring and connector are intact, remove the level sensor from the tank and inspect the float arm for mechanical binding or crystalline deposits; clean or replace the sensor as needed.
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6
Measure sensor resistance at the terminals across the expected float travel range and compare to OEM specifications.
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7
Replace the level sensor if it is mechanically stuck, out of resistance spec, or corroded beyond cleaning; repair any confirmed wiring fault.
Vehicles where we've handled P2C30
Platforms in our catalogue with confirmed P2C30 coverage.
Related powertrain codes
- P2C20 — Turbocharger/Supercharger Boost Control A Circuit Open
- P2C21 — Turbocharger/Supercharger Boost Control A Circuit Low
- P2C22 — Reductant Pump Performance
- P2C2B — Turbocharger/Supercharger Boost Control B Circuit Open
- P2C2C — Turbocharger/Supercharger Boost Control B Circuit Low
- P2C31 — Turbocharger/Supercharger Intake Air Flow Control Circuit Open
Frequently asked questions
Will P2C30 affect SCR dosing directly?
Not immediately. Dosing is primarily controlled by the NOx and pressure feedback loops, not the level sensor. However, a stuck-full reading can allow the tank to run dry without warning, which will stop dosing entirely.
Can I clean the sensor instead of replacing it?
If the fault is DEF crystal buildup on the float or sender contacts, soaking the sensor in warm water to dissolve the crystals can sometimes restore function. If the element itself is corroded or failed, replacement is required.
Is P2C30 specific to one sensor in the tank assembly?
On most platforms the level, temperature, and quality sensors are packaged as a single unit. Check whether the OEM supplies the level sender separately or only as part of the full sensor module.
Could this code appear immediately after refilling the DEF tank?
If the float was stuck in a low position due to crystallisation and the new fluid partially dissolved the crystals, movement of the float could expose an electrical fault that was previously masked. This is a known diagnostic nuance.
Disabling P2C30 in software
RaceTune can permanently disable P2C30 — 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 P2C30 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
- Bosch MG1CP002 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.
Got P2C30 in your scan?
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