DTC code
P0400
EGR A Flow
Technical guide
Symptoms
- Check engine light
- rough idle
- failed emissions
- poor fuel economy
Probable causes
- EGR system flow malfunction
- EGR valve stuck
- EGR solenoid fault
- EGR differential pressure sensor fault
- EGR pipe blocked
Diagnostic steps
- Remove and clean EGR valve - carbon buildup is most common cause.
- Test EGR solenoid.
- Check EGR differential pressure sensor.
- Inspect EGR pipe/cooler.
- Replace EGR valve if cleaning fails.
Brand-specific notes (Peugeot/Citroen)
Peugeot/Citroen · 206/207/306/307/Berlingo · 1.4/1.6/1.8/2.0 petrol
Symptoms
- Check engine light
- rough idle
- failed emissions test
- poor fuel economy
Probable causes
- EGR valve sticking/blocked with carbon
- EGR solenoid failed
- EGR differential pressure sensor fault
- EGR pipe blocked
Diagnostic steps
- Remove and clean EGR valve with EGR cleaner.
- Test EGR solenoid operation.
- Check EGR differential pressure sensor.
- Inspect EGR pipe for blockage.
- Replace EGR valve if cleaning fails.
Cross-checked technical synthesis (QA). It does not replace the manufacturer's procedure.
AI here is a librarian: this page shows only what mechanics confirmed, or says “unknown”. It never suggests a diagnosis — MECCANIC interprets the code, never your car.
0 confirmed cases on P0400
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