P2457Powertrain
Powertrain · SAE
EGR Cooling System Performance
Meaning
The EGR cooler is not reducing exhaust gas temperature to within expected limits. The ECU compares EGR inlet and outlet temperatures; if the temperature drop is insufficient, this fault is set. Applies exclusively to diesel engines with cooled EGR systems.
Common causes
- EGR cooler fouled internally with soot and carbon (most common)
- Coolant flow restriction through the EGR cooler circuit
- Failed coolant thermostat keeping coolant too hot
- Internal coolant-to-exhaust leak inside the EGR cooler
Symptoms
- MIL illuminated
- Elevated EGR gas temperature reducing NOx control efficiency
- White smoke from exhaust if coolant leaks into EGR
- Possible coolant loss
Severity
High severity on diesel engines: an inefficient EGR cooler increases NOx emissions and, in the event of an internal leak, can introduce coolant into the combustion chamber.
What to do
- Compare EGR inlet vs. outlet temperatures with a scan tool during EGR operation
- Check coolant level and inspect for contamination
- Inspect EGR cooler externally for leaks
- Flush or replace the EGR cooler