P3870moderate severityPowertrain
Electronic EGR Cooler Bypass Valve Stuck
on 2010 Audi A3 2.0L TDI I4 · FWD
What this code means
The electronic EGR cooler bypass valve that routes exhaust gas around or through the EGR cooler is stuck.
Symptoms
- Check Engine Light
- EGR gas temperature incorrect
- Higher NOx emissions
- Reduced engine performance
- EGR cooler may overheat or underperform
- Intake manifold carbon buildup changes
Common causes
- Carbon buildup on valve
- Actuator motor failure
- Valve mechanism corroded
- Wiring fault
- Exhaust condensation causing corrosion
Diagnostic steps
- Command EGR cooler bypass valve via scan tool
- Monitor EGR gas temperature upstream and downstream of cooler
- Inspect valve actuator operation
- Test valve position sensor
- Check for carbon deposits on valve
Repair notes
Replace EGR cooler bypass valve. Clean carbon deposits from EGR passages. Inspect EGR cooler for leaks.
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