This code usually needs a check soon to find out what is wrong.
Trouble codes · P0402
P0402 meaning
EGR A Flow Excessive Detected
The same first verdict Car Assist shows from this code alone, before a diagnosis. The code does not tell the app whether the warning light is flashing.
What this code doesn’t tell you
A code says where the car noticed a problem. It does not prove which part failed, whether the fault is still present, or what repair this car needs. The engine, other codes, freeze frame and live readings matter.
Usual causes, most likely first
The order is a starting point across cars; the exact engine and its readings can change it.
- EGR valve stuck open or not closing fully
- Faulty EGR position or pressure sensor
- EGR control fault
What you can check
Note rough idle or stalling when coming to a stop. Keep other stored codes; have the valve's movement tested before replacing it.
Words the car uses
- Stored codes
- Faults the car has confirmed and saved. They help explain a check-engine light, but a code alone does not prove which part needs replacing.
- Freeze frame
- A snapshot of the engine's readings when a fault was recorded. It helps show the conditions that caused the fault, even if the car now seems fine.
- Readiness monitors
- The car's own checks of its emissions systems. An unfinished check means the car has not tested that system yet, so a clean code scan may miss a fault.
- Exhaust recirculation (EGR)
- A system that sends some exhaust back into the engine to reduce emissions. Comparing requested and measured readings can help spot a stuck valve.
Find out what’s causing yours
Car Assist reads your car through an OBD-II adapter and your iPhone. Its assistant uses the codes, freeze frame and live readings to work through the likely cause with you.