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OBD-II · Engine and powertrain (P)

P2457

EGR cooler efficiency below threshold

What it means

The EGR cooler is not cooling the recirculated exhaust gas enough, judged by a temperature sensor after the cooler.

Symptoms

  • engine warning light
  • usually no noticeable change
  • coolant loss or white smoke if the cooler is leaking internally

Likely causes, most likely first

Likely causes, most likely first
No.Cause
01EGR cooler clogged with soot
02EGR cooler bypass flap stuck open or its actuator faulty
03faulty temperature sensor after the cooler
04low coolant or air in the cooling system
05EGR cooler leaking internally

What to check, step by step

  1. 01Check coolant level and look for unexplained coolant loss or white smoke.
  2. 02Check the EGR cooler bypass flap and its actuator (vacuum or electric) move freely.
  3. 03Compare the EGR temperature reading with the engine cold and at operating temperature.
  4. 04Pressure-test the cooling system; an internally leaking cooler must be replaced.
  5. 05Replace or clean a blocked cooler.