P0777Pressure Control Solenoid B Stuck On
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- Harsh shift jolt, transmission ties up
- Limp mode in a fixed gear
- Check engine light
- Likely causes
- LikelySpool or pressure valve sticking
- PossibleClutch stuck or piston hanging
- PossibleContaminated fluid (debris after clutch damage)
- RareSoftware or false setting
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €400 – €5,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.