Powertrain, generic (extended)

P248F EGR Cooler Bypass Control Circuit Range/Performance (Bank 2)

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

With P248F the bank 2 bypass circuit is electrically sound, yet the flap does not do what the controller asks: it lags behind the setpoint, stops short of its end position or switching shows no effect on the gas temperature after the cooler. No manufacturer publishes a bank 2 version of this check. On bank 1 (P245B) GM's 2017 Duramax logic compares commanded and measured flap position and fails above a 16 % deviation, while Ford's 2023 diesels move the flap on purpose and expect a clear temperature response. A second bank would be judged the same way. Sticking from soot and oil carbon, a tired return spring, weak vacuum on pneumatic versions or wrong position feedback are the usual reasons. If the flap is later found fixed in place, the stuck code P24A6 may follow.

Likely causes

Bypass flap on bank 2 sluggish from soot and carbon

Leaking vacuum line or weak vacuum on pneumatic actuators

Bank 2 position feedback reading off

Symptoms

Check engine light on
Often no noticeable change in driving

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€100–900

Time0.5–4 h

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

Parts involved

egr cooler bypass valve b2

Related codes

P245B P248E P2498 P24A6

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