P0401: EGR Insufficient Flow Detected
P0401 means the exhaust gas recirculation system isn't flowing enough. Carbon buildup is the usual culprit — cleaning first, replacement only if that fails.
Severity: moderate · System: Powertrain · Safe to drive: usually, short-term. Not urgent, but will fail emissions inspection. Cleaning often fixes it.
Symptoms
- Rough idle
- Pinging under acceleration
- Failed emissions test
Common causes
- Clogged EGR valve
- Blocked EGR passages
- Bad EGR sensor
Fair repair prices
| EGR valve cleaning | $100–$250 |
|---|---|
| EGR valve replacement | $250–$700 |
| EGR passage cleaning (labor-heavy) | $300–$800 |
Ranges are US market averages (parts and labor). If your shop's quote is above the high end, ask for a line-item breakdown or run it through the invoice checker.
Other codes
- P0300 — Random / Multiple Cylinder Misfire Detected
- P0301 — Cylinder 1 Misfire Detected
- P0420 — Catalyst System Efficiency Below Threshold (Bank 1)
- P0430 — Catalyst System Efficiency Below Threshold (Bank 2)
- P0171 — System Too Lean (Bank 1)
- P0174 — System Too Lean (Bank 2)
- P0442 — Evaporative Emission Control System Leak (Small)
- P0455 — Evaporative Emission Control System Leak (Large)