P2879Clutch B Performance/Stuck Disengaged
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Reverse or even gears missing
- Engine speed rises without thrust
- MIL and limp mode
- Likely causes
- LikelyWorn or glazed clutch B slipping under load
- PossibleInsufficient apply pressure from valve body, pump or regulator
- PossibleClutch B actuator motor or its drive failed
- RareWiring fault or control unit not commanding the clutch
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €100 – €4,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.