P2457EGR Cooler A Efficiency Below Threshold
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Malfunction indicator lamp on
- Higher NOx, sometimes reduced EGR or power
- Coolant loss or white smoke if the cooler is also leaking
- Likely causes
- LikelyCooler passages fouled with soot and lacquer
- PossibleBypass flap stuck in bypass position or bypass module loose
- PossibleEGR outlet temperature sensor reading too high
- RareLow coolant level or poor coolant flow through the cooler
- RareMonitor software misjudging efficiency (known on some trucks)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.