P0401 — EGR Insufficient Flow Detected

P0401 means your Exhaust Gas Recirculation (EGR) system isn't flowing enough exhaust back into the intake. Carbon buildup in the EGR valve or passages is the most common cause.

Cost range: $50–$600. Severity: low. Safe to drive? Yes, but expect rough idle and emissions failure.

Most common causes of P0401

1. Carbon-clogged EGR valve — Clean with throttle body cleaner — saves $300+. ($10–$50)
2. Clogged EGR passages — Requires intake removal on some engines. ($200–$500)
3. Failed EGR valve — If cleaning doesn't fix it, replace. ($150–$600)
4. Bad DPFE sensor (Ford) — Specific to many Ford vehicles. ($50–$150)

Symptoms drivers report with P0401

• Rough idle
• Pinging on acceleration
• CEL