P0777 means Pressure Control Solenoid B Stuck On. Pressure control solenoid B appears to be stuck on, holding pressure when it should change it. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0777 means
Electronically controlled automatics are run by a transmission control module (TCM), a separate box or part of the engine computer. It reads speed sensors, the range sensor and fluid temperature to decide when to shift, and drives solenoids that apply clutches and the torque converter clutch. Many basic code readers only show the generic P0700; a scan tool that reads the transmission module shows the specific fault. Check fluid level and condition first, since low or burnt fluid causes many transmission codes.
P0777 symptoms
- Harsh or soft shifts
- Slipping
- Limp mode
- Check engine light
Common causes of P0777
- Debris holding the solenoid or valve open
- Failed solenoid
- Valve body wear
How to diagnose P0777
- Check transmission fluid level and condition first
- Check line pressure with a gauge
- Watch commanded vs actual pressure on a scan tool
- Inspect the solenoid and valve body for debris
Can you drive with P0777?
Limit driving; pressure problems can quickly damage clutches.
P0777 tips
A stuck-on pressure control solenoid can cause harsh engagement into drive and reverse; check the fluid and pan debris first.
Will P0777 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0777 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0778 | Pressure Control Solenoid B Electrical |
| P0745 | Pressure Control Solenoid A |
| P0868 | Transmission Fluid Pressure Low |
Guides that help
When it is more than a sensor
If the fault turns out to be internal (worn clutches, a failed converter or a damaged valve body), compare a rebuild with a replacement in transmission rebuild vs replacement and transmission replacement cost, identify your unit with what transmission do I have?, and browse our transmissions.
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