P0777
Pressure Control Solenoid B Stuck On
Pressure control solenoid B does not release line pressure when commanded — output pressure remains at maximum, leading to harsh shifts and elevated stress on the clutch packs and seals.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: hard
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Common causes
Ordered by how often each turns out to be the cause.
- Solenoid stuck open by debrisCommon
- Contaminated ATF clogging the pressure control valvePossible
- Carbon or debris buildup preventing free movementLess likely
Parts involved
- Pressure Control Solenoid B
- Valve Body
P0777 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.