Exhaust gas recirculation
P0401
Exhaust Gas Recirculation Flow Insufficient Detected
The system that feeds a little exhaust back into the engine to lower emissions isn't flowing the way the computer expects. Too little flow almost always means carbon is blocking the valve or its passages.
Fine to drive
Can I keep driving? Yes, in most cases. It won't hurt the car in the short term, but get it fixed. A check engine light that's already on can't warn you about a new problem. It's safe to drive. You may notice pinging or a rough idle, and it will fail an emissions test.
Common causes
- Carbon blocking the EGR valve or its passages
- A failed EGR valve or position sensor
- A vacuum or wiring fault
Listed roughly from most to least likely. The same code can have different causes on different cars.
What to do
- Have the EGR valve and passages checked for carbon.
- Clean or replace the valve.
- Check the wiring and any vacuum lines.
General guidance. Your owner's manual wins. If a red warning light is on or the car drives differently, stop safely and get help.
Related codes
- P0400Exhaust Gas Recirculation Flow
- P0402Exhaust Gas Recirculation Flow Excessive Detected
- P0403Exhaust Gas Recirculation Control Circuit
- P0404Exhaust Gas Recirculation Control Circuit Range/Performance
- P0405Exhaust Gas Recirculation Sensor "A" Circuit Low
Track this automatically in Tagwell Auto
Tagwell Auto keeps your car's service dates and mileage, so when a code shows up you know what was done last. With a Bluetooth reader for the car's diagnostic port (called OBD-II), the phone app can read the code itself.