Powertrain, generic (extended)

P2878 Clutch B Disengagement Time Too Fast

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2878 reports that clutch B lets go sooner or more abruptly than the release ramp held in the control unit. During a powershift the outgoing clutch has to keep carrying torque until the incoming one has taken over; if clutch B drops out early, the engine flares for a moment and the next gear arrives with a jolt, mostly on shifts away from reverse and the even gears. No manufacturer publishes detection criteria for P2878; CARB 13 CCR 1968.2 is the legal basis. Ford's DPS6 summary shows why timing errors arise on dry designs: a motor turns a screw-driven fulcrum, hall sensors count its travel from an end stop, and a spring pulls the clutch open as soon as the motor lets go. A lost position count, a weak hold or adaptation values that no longer match the linings all shorten the release.

Likely causes

Clutch B adaptation values no longer matching the linings
Actuator position count lost or misread by the hall sensors
On wet systems a clutch B valve venting pressure too quickly
Low fluid level or aerated fluid

Symptoms

  • Brief engine flare followed by a jolt when shifting
  • Harsh shifts out of even gears or reverse
  • Warning lamp, firmer substitute shift program

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–3,000
Time0.5–8 h

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

Parts involved

clutch bclutch actuator btransmission fluid

Related codes

P2877P2876P2870P2879P287A

References: law.cornell.edu, newtonnet.co.uk, gsi.ext.gm.com.