P3834moderate severityPowertrain
DEF Supply Pump Pressure Low
on 2010 Audi A3 2.0L TDI I4 · FWD
What this code means
The DEF supply pump is not generating sufficient pressure to properly atomize DEF through the dosing valve.
Symptoms
- DEF system malfunction light
- Insufficient DEF dosing
- SCR efficiency reduced
- Potential derate
- Check Engine Light
- Poor atomization of DEF spray
Common causes
- DEF pump wear
- DEF filter clogged
- Air in DEF supply lines
- DEF line leak
- DEF frozen in lines or tank
Diagnostic steps
- Check DEF supply pressure with scan tool
- Inspect DEF filter condition
- Check DEF lines for air leaks
- Verify DEF line heaters working
- Test pump motor operation
Repair notes
Replace DEF supply pump or filter. Purge air from DEF lines. Check and repair DEF line heaters for cold weather operation.
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