P3881high severityPowertrain
Lean NOx Trap (LNT) Desulfation Failure
on 2009 Audi A3 2.0L TDI · FWD
What this code means
The lean NOx trap desulfation process has failed to restore NOx conversion efficiency. The LNT requires periodic high-temperature desulfation to remove sulfur compounds.
Symptoms
- Check Engine Light
- Increased NOx emissions
- LNT warning
- Failed emissions test
- Reduced power may occur
- Fuel economy decrease from failed desulfation attempts
Common causes
- Fuel sulfur content too high
- LNT catalyst degradation
- Exhaust temperature insufficient for desulfation
- Fuel injection issue during desulfation
- LNT poisoned beyond recovery
Diagnostic steps
- Check LNT NOx efficiency before and after desulfation attempt
- Monitor exhaust temperature during desulfation
- Check fuel quality
- Inspect fuel injectors for desulfation function
- Review desulfation attempt history
Repair notes
Attempt forced desulfation at controlled temperatures. Replace LNT if desulfation cannot restore efficiency. Use ultra-low sulfur diesel fuel.
Other Powertrain codes on this vehicle
P0001
Fuel Volume Regulator Control Circuit/Open
P0002
Fuel Volume Regulator Control Circuit Range/Performance
P0003
Fuel Volume Regulator Control Circuit Low
P0004
Fuel Volume Regulator Control Circuit High
P0010
Intake Camshaft Position Actuator Circuit/Open Bank 1
P0011
Intake Camshaft Position Timing Over-Advanced Bank 1
P0012
Intake Camshaft Position Timing Over-Retarded Bank 1
P0013
Exhaust Camshaft Position Actuator Circuit/Open Bank 1
P0014
Exhaust Camshaft Position Timing Over-Advanced Bank 1
P0015
Exhaust Camshaft Position Timing Over-Retarded Bank 1