Powertrain, generic (extended)

P2457 EGR Cooler A Efficiency Below Threshold

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

The EGR cooler is supposed to bring recirculated exhaust close to coolant temperature; P2457 says cooler A no longer removes enough heat, as CARB requires diesel systems to detect. GM rates efficiency as the drop across the cooler divided by the gap between inlet gas and coolant; in the 2017 tables the Duramax fails below 60 %, the MDE engine family below 50 %, each after two trips. Ford's 6.7 L diesel instead watches the outlet gas: above coolant plus 70 °C in 2013 and plus 88 °C in 2023 for 12 s, with the bypass in cooling position; gasoline engines with cooled EGR use a flow ratio. Ford traced P2457 on 2018 to 2019 F-150 3.0 L diesels to loose screws in the bypass module, and Hino fixed 2012 trucks by software. Soot fouling and a bypass flap stuck in bypass are common; cooler B is P241F.

Likely causes

Cooler passages fouled with soot and lacquer
Bypass flap stuck in bypass position or bypass module loose
EGR outlet temperature sensor reading too high
Low coolant level or poor coolant flow through the cooler
Monitor software misjudging efficiency (known on some trucks)

Symptoms

  • Malfunction indicator lamp on
  • Higher NOx, sometimes reduced EGR or power
  • Coolant loss or white smoke if the cooler is also leaking

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–2,500
Time0.5–8 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

egr cooleregr temperature sensor

Related codes

P241FP24A5P245BP0401P2425

References: gsi.ext.gm.com, fordservicecontent.com, static.nhtsa.gov, fordservicecontent.com.