P0401 Code: Exhaust Gas Recirculation (EGR) Flow Insufficient
P0401 means the EGR system isn’t flowing enough exhaust gas back into the intake, usually from carbon blockage.
- Applies to
- All OBD-II vehicles (any make or model)
- Est. repair cost
- $80 – $500
- Time to fix
- 1-3 hours
What it means
Common causes are carbon-clogged EGR passages or valve, a stuck EGR valve, or a faulty EGR position/DPFE sensor. This is a generic OBD-II powertrain code defined in the SAE J2012 standard, so it applies to virtually any 1996-or-newer OBD-II vehicle — cars, trucks, and modern fuel-injected motorcycles — from any manufacturer (Toyota, Honda, Ford and the rest). Read it with any OBD-II scanner; the meaning is the same across brands, though the exact repair can vary by engine.
Symptoms
- Check engine light on
- Pinging/knock under load; rough idle
- Failed emissions test
How to fix it
- 1
Clean the EGR system
1. Remove and clean the EGR valve and passages of carbon. 2. Check the EGR position/DPFE sensor. 3. Reinstall, then clear the code.
Frequently asked questions
Can I just clean the EGR for P0401?
Often yes — carbon blockage is the usual cause. Clean the valve and passages first; replace the valve or sensor only if cleaning doesn’t fix it.
Last updated July 16, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.