Powertrain, generic (extended)

P2856 Clutch B Pressure Charge Performance

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2856 flags too much pressure at clutch B, the even-gear clutch in GM's and Ford's dual-clutch layouts. For the Corvette unit GM checks clutch 2 with the same high-side logic as clutch 1, including the hold-pressure case: an open clutch held at its standby pressure must not rise well above that point, because it would then pass torque while the other clutch is driving. A Type A code follows, and the even clutch recovery routine is requested. Ford's 2024 summary lists P2856 on the TR9070 for even clutch pressure above target. Both clutches carrying torque at once can make the car shudder or brake itself, so continuing on the odd gears with clutch B open is the likely fallback.

Likely causes

Clutch B pressure control valve hanging in a high-pressure position
Safety shutdown valve for clutch B not venting
Clutch B pressure sensor reading high within its range

Symptoms

  • Shudder or binding during shifts
  • Even gears blocked, emergency program
  • Warning lamp

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€200–4,000
Time1–12 h

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

Parts involved

clutch bclutch actuator btransmission fluid

Related codes

P2855P2854P285AP0869P0846

References: gsi.ext.gm.com, fordservicecontent.com.