Powertrain, generic (extended)

P278F Clutch B Adaptive Learning at Limit

Check engine lightOn
EmissionsNot relevant
Drive cycleRequired
Limp modePossible

P278F flags that the learned values for clutch B have run out of room. In a dual-clutch gearbox this is usually the clutch for the even gears; the controller keeps adjusting its touch point and pressure or travel so that handovers between the two clutches stay seamless, and stores the code once a correction hits its end stop. No manufacturer documents P278F publicly with set conditions; CARB requires such transmission functions to be monitored. What the clutch A sibling P2789 shows in Allison's bulletins applies here too: software and an implausible engine torque signal are checked first, worn or damaged plates second. On dry clutches, wear increases the release travel until the learned range is used up. Expect shudder on even gears, slow or rough handovers and a warning lamp; P2788 is the system-level code.

Likely causes

Worn clutch B lining or plates shifting the touch point
Clutch adaptation not reset or relearned after repair
Clutch B actuator or release mechanism sticking or losing pressure
Outdated software or inaccurate engine torque information

Symptoms

  • Shudder or slip when an even gear takes over
  • Rough or slow shifts between gears
  • Transmission warning lamp

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€80–2,500
Time0.5–8 h

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

Parts involved

dual clutch btcm

Related codes

P2789P2788P27F3

References: law.cornell.edu, en.wikipedia.org, static.nhtsa.gov.