What the dictionary says
EGR A Flow Insufficient Detected
Source: generic entry in the MIT-licensed dtc-database · view source file
P0401 is a generic OBD fault code. The fault-code dictionary we use defines it as "EGR A Flow Insufficient Detected". Below: the source entry, manufacturer entries, related codes and the terms explained.
Manufacturer entries in the dictionary
Audi
Restriction in the EGR passages usually caused by carbon buildup, The EGR Valve is defective, Lack of proper vacuum or electrical signal to the EGR valve, Malfunctioning EGR Vacuum supply solenoid, Lack of proper EGR system feedback to the computer from the: Manifold Absolute Pressure Sensor (MAP), Differential EGR Pressure Feedback Sensor (DPFE), EGR Valve Position Sensor (EVP), EGR Temperature Sensor
Source file · Listed as written in this source file. Not ranked; a workshop must confirm what applies to your car.
Reading the code P0401
- First character: P: Powertrain (engine, transmission and ignition)
- Second character: 0: a generic code defined by SAE, meant to mean the same thing on every make
- Last three characters: 401: The specific fault within that category.
Reference: On-board diagnostics (Wikipedia)
Terms in this code
- EGR (exhaust gas recirculation): A system that sends part of the exhaust gas back into the engine to reduce nitrogen oxide (NOx) emissions. More
Related codes
Singapore notes
LTA's periodic inspection checks a car's exhaust emissions and noise against the prevailing standards, as well as brakes, steering, lights and structure. Cars under 3 years old have no periodic inspection, cars aged 3 to 10 years are inspected every 2 years, and cars over 10 years every year. The dictionary does not say how this code affects an inspection, so ask the inspection centre or a workshop. LTA: vehicle inspection
Need a workshop? See workshops owners recommend or the Subaru list.
What this page does not tell you
The dictionary does not establish repair costs, how likely each cause is, or whether the car is safe to drive. Get a workshop diagnosis and a written quote before paying for parts.
For a make-specific answer, use the lookup below with your make and model. The dictionary has 93 Subaru-specific entries among 18,805 in total.