Powertrain, generic (extended)

P241F EGR Cooler B Efficiency Below Threshold

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

Engines with two EGR loops can carry two coolers; P241F flags that the second one, cooler B, no longer removes enough heat from the recirculated gas. GM's 2020 diesel tables (20OBDG04) pin cooler B to the low-pressure EGR path: efficiency is derived from the gas temperatures before and after the cooler, corrected for flow, averaged and failed below 50 percent, a Type B fault (two trips) with coolant between 60 and 130 °C. The high-pressure cooler is checked there under P2457 against 72.61 percent. Ford monitors its single cooler only under P2457, via outlet temperature over coolant temperature. CARB demands detection of insufficient EGR cooling. Expect higher NOx and a fouled or bypassing cooler.

Likely causes

Soot or lacquer deposits on the cooler passages
Drifting EGR temperature sensor before or after the cooler
Weak coolant flow through the cooler (air pocket, thermostat, pump)
Cooler bypass flap not closing

Symptoms

  • Check engine light after two trips
  • Higher NOx, possibly more frequent DPF regenerations

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–1,800
Time1–6 h

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

Parts involved

egr cooler b

Related codes

P2457P245AP245BP0401P2425

References: gsi.ext.gm.com, fordservicecontent.com, law.cornell.edu.