All codes
P0401Emissions System
EGR Insufficient Flow Detected
Fix P0401 EGR flow code. Learn about the exhaust gas recirculation system and how to restore proper flow.
What you may notice
Symptoms
- 01Check engine light on
- 02Engine knock or ping under load
- 03Rough idle in some cases
- 04Failed emissions test
- 05Slight performance decrease
Where to look first
Common causes
- 01Clogged EGR passages
- 02Carbon buildup on EGR valve
- 03Faulty EGR valve
- 04EGR position sensor failure
- 05Vacuum supply issues
Step by step
What to check and repair
- 01Clean EGR valve and passages
- 02Replace EGR valve if damaged
- 03Clean intake manifold EGR ports
- 04Check EGR position sensor
- 05Verify vacuum supply to EGR
What Does P0401 Mean?
P0401 indicates that the EGR (Exhaust Gas Recirculation) system is not flowing enough exhaust gas back into the intake manifold.
EGR Purpose
The EGR system reduces NOx emissions by recirculating a small amount of exhaust gas to lower combustion temperatures.
Common Issue
Carbon buildup is the most frequent cause. EGR passages and valves get clogged with carbon deposits over time.