Powertrain, generic · Transmission

P0777 Pressure Control Solenoid B Stuck On

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Pressure control solenoids are current-controlled proportional valves, and what B and C mean depends on the design: on GM's clutch-to-clutch automatics they are the pressure valves of clutches 2 and 3, on GM's CVT B is primary pulley pressure and C line pressure, on Jatco CVTs B is the secondary pressure valve, on Saab's AF40 B and C are clutch valves SLC1/SLC2. P0777 means the valve is electrically fine but pressure stays applied – the off-going clutch does not release. GM's 9-speed flags clutch 2 slip below 50 rpm for 0.8 s on loaded downshifts, the 8-speed uses a torque and inertia phase test, Allison 25 rpm or less – all after one trip. GM's Honda-built five-speed cannot always separate it from P0746 and stores both. Harsh shift jolts, tie-up and a default gear follow.

Likely causes

Spool or pressure valve sticking
Clutch stuck or piston hanging
Contaminated fluid (debris after clutch damage)
Software or false setting

Symptoms

  • Harsh shift jolt, transmission ties up
  • Limp mode in a fixed gear
  • Check engine light

Repair estimate

DifficultyHardWorkshop job
Parts and labour€400–5,000
Time2–14 h

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

Parts involved

pressure control solenoidtransmission valve bodytransmission clutchestransmission control module

Related codes

P0776P0778P0747P0797P2715

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