P2802
Range Sensor B Circuit LowP2802 is a generic OBD-II powertrain diagnostic trouble code: Range Sensor B Circuit 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 P2802 means
P2802 is stored when the ECM or SCR control module detects that the voltage or signal from the reductant (DEF/AdBlue) level sensor circuit is above the expected maximum threshold. The reductant level sensor is located in the DEF tank and provides continuous feedback on fluid level to enable accurate low-level warnings and prevent dry dosing.
A high-circuit condition typically points to a short to voltage in the sensor signal wire, an open return or ground circuit, or an internal sensor failure that drives the output rail-high. Because the sensor circuit is part of the broader reductant quality and level monitoring system, a fault here can suppress accurate level reporting and disable DEF low-level alerts.
In many calibrations this code alone will not immediately derate the engine, but if the level cannot be verified and other reductant faults are also present, the vehicle may enter a derate or no-start strategy after a set number of warm-up cycles. Prompt diagnosis of the wiring before sensor replacement is important, as connector corrosion from DEF crystallization is a frequent root cause.
Common causes
Most-frequently reported root causes when P2802 is logged.
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1
Short to battery voltage on the reductant level sensor signal wire.
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2
Open or high-resistance ground/return circuit for the sensor.
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3
DEF crystallization causing corrosion in the sensor connector, driving signal high.
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4
Failed reductant level sensor with internal open creating a high-impedance output read as high voltage.
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5
Damaged wiring harness routed near heat sources in the DEF tank area.
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6
Faulty SCR control module input circuit holding the line high.
Symptoms drivers notice
How to diagnose P2802
A typical diagnostic flow when this code is present.
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1
Retrieve all DTCs and note any concurrent reductant quality, temperature, or dosing faults.
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2
Inspect the DEF tank level sensor connector for DEF crystal contamination and corrosion.
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3
Measure the signal wire voltage with the sensor disconnected; a high voltage with sensor unplugged indicates a short to power in the harness.
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4
Check the sensor ground/return circuit for continuity to the control module.
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5
Verify sensor supply voltage is within specification.
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6
Test or substitute the level sensor if wiring checks are satisfactory.
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7
Inspect the SCR control module connector for moisture or corrosion before suspecting module failure.
Vehicles where we've handled P2802
Platforms in our catalogue with confirmed P2802 coverage.
Related powertrain codes
Frequently asked questions
Can DEF crystallization cause P2802?
Yes. DEF evaporates and leaves urea crystals that can bridge connector pins, create unexpected resistance or shorts, and drive the sensor circuit to an abnormal high state.
Is P2802 different from a low DEF level warning?
Yes. P2802 is an electrical circuit fault, not an indication that fluid level is actually low. The sensor's ability to report level accurately is compromised.
Will this code cause a vehicle derate right away?
Typically not immediately; most calibrations allow several drive cycles before enforcing a derate. However, if other reductant faults are also set, derate can occur sooner.
How do I clean DEF crystal contamination from the connector?
Use warm distilled water to dissolve urea crystals, dry thoroughly, and apply dielectric grease before reconnecting. Avoid using compressed air alone as it can push crystals deeper.
Disabling P2802 in software
RaceTune can permanently disable P2802 — 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 P2802 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
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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