P0401 – EGR Flow Insufficient
Want to confirm the real cause of this fault code?
A high‑quality OBD2 scanner gives you live data, fuel trims, sensor readings and freeze‑frame information — exactly what you need to verify the root cause of this code with confidence.
Symptoms
- Rough idle
- Hesitation
- Poor acceleration
- High NOx emissions
- Check engine light
Causes
- Clogged EGR passages
- Faulty EGR valve
- Vacuum leak
- Faulty DPFE sensor
- Carbon buildup
Diagnosis
- Inspect EGR valve
- Check vacuum lines
- Test DPFE sensor
- Inspect passages
- Scan live data
Repair
- Clean EGR passages
- Replace EGR valve
- Fix vacuum leaks
- Replace DPFE sensor
- Remove carbon buildup