This code usually needs a check soon to find out what is wrong.
Trouble codes · P2457
P2457 meaning
EGR Cooler A Efficiency Below Threshold
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.
- Clogged or leaking EGR cooler
- EGR cooler bypass valve fault
- Low coolant or cooling system fault
What you can check
With the engine fully cold, check the coolant reservoir level with its cap closed; have a falling level, white exhaust smoke or a sweet smell checked. Usually a temperature warning needs a stop when safe and the engine switched off.
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.
- Coolant
- The liquid that carries heat away from the engine. Its temperature helps show whether the engine warms up properly. An overheating warning usually needs a stop when safe and the engine switched off.
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.