P2457
EGR Cooler Performance
The EGR cooler does not lower exhaust gas temperature as expected — typically internal coolant fouling, a partial blockage, or a cracked cooler that mixes coolant with exhaust gas.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
Symptoms
- Check engine light on
- Pinging or knocking under load
- Power loss and hesitation
- Possible rough idle
- Failed emissions inspection (NOx)
Common causes
Ordered by how often each turns out to be the cause.
- Cooler internally clogged with sootCommon
- Cooler cracked, coolant entering exhaustPossible
Parts involved
- EGR Cooler
- EGR Temperature Sensor
P2457 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.