P2BAD
PPowertrainNOx Exceedance: Root Cause Unknown
What does this code mean?
Severity : MediumP2BAD indicates that NOx emissions exceed the permitted limit and the ECU cannot identify the exact cause. It uses the NOx sensors to detect the exceedance, but no other specific fault explains the problem. This code often triggers AdBlue warnings and progressive restrictions on the vehicle.
Symptoms
- Check engine or AdBlue warning light on.
- Warning message with a countdown before engine start is restricted.
- Possible speed or power limitation.
- Often no drivability symptom at first.
Possible causes
- Poor quality or diluted AdBlue/DEF.
- Fouled AdBlue injector or insufficient dosing.
- Faulty or drifting upstream or downstream NOx sensor.
- Fouled or aged SCR catalyst.
- Clogged EGR valve increasing engine-out NOx.
- Exhaust leak distorting readings.
Diagnosis and repair
- Read all stored codes, including in the SCR control unit.
- Check AdBlue level and quality.
- Compare NOx sensor readings in live data.
- Test AdBlue injector dosing and EGR valve operation.
- Repair the faulty part, clear the code and road test.
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Code
P2BAD
Category
Powertrain
Prefix
P
Standard
OBD-II / SAE J2012