Powertrain, generic (extended)

P2879 Clutch B Performance/Stuck Disengaged

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P2879 is set when clutch B does not reach the torque it is asked for, or stays open altogether, so a large speed difference remains across it. No manufacturer publishes a test written for P2879. Mitsubishi shows the method on the clutch A sibling P2871 of the 2023 Outlander PHEV: once parallel mode has run for 2 s, the PHEV-ECU counts phases in which input and output differ by at least 75 rpm over 2 s, and the eighth such phase sets the code with MIL. Ford's 2012 DPS6 summary files the matching clutch B motor fault as P07A4, functionally stuck off; there clutch B drives reverse and the even gears. A car with this fault may refuse reverse, skip 2nd, 4th and 6th or flare without pulling. Worn linings, low apply pressure, a failed actuator motor and wiring faults are the usual suspects.

Likely causes

Worn or glazed clutch B slipping under load
Insufficient apply pressure from valve body, pump or regulator
Clutch B actuator motor or its drive failed
Wiring fault or control unit not commanding the clutch

Symptoms

  • Reverse or even gears missing
  • Engine speed rises without thrust
  • MIL and limp mode

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–4,000
Time0–10 h

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

Parts involved

clutch bclutch actuator bvalve body

Related codes

P2871P2875P2878P287AP07A4

References: mitsubishitechinfo.com, newtonnet.co.uk, law.cornell.edu.