OBD-II trouble code
P0777: Pressure Control Solenoid "B" Stuck On
The transmission control module detected that pressure control solenoid B is stuck in the on position, so its pressure stays high. Expect harsh, firm shifts — address it promptly to protect the clutches and internals.
Quick facts
- System
- Powertrain
- Category
- Transmission / Pressure Control
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $150 – $900
- DIY difficulty
- Shop recommended
What does P0777 mean?
P0777 sets when the transmission control module (TCM) or PCM commands pressure control solenoid "B" to change state and the solenoid stays stuck in its energized, or "on," position. Rather than modulating pressure as commanded, the solenoid holds its circuit at a fixed pressure that stays high.
Pressure control solenoid B is a second pressure-regulating solenoid in the valve body; depending on the transmission it may control a specific clutch circuit or a secondary pressure. When it's stuck on and pressure can't be reduced, the affected shifts land hard — the transmission feels firm and abrupt. That's the opposite failure mode from P0776, where the solenoid is stuck off and can't build pressure at all.
The cause is often mechanical rather than electrical. The coil frequently tests fine, and the real problem is debris, varnish, or a burr holding the valve in the applied position so it won't return. Dirty or degraded fluid promotes exactly this kind of sticking, which is why fluid condition matters and a fluid and filter service is a sensible first step. Diagnosis then moves to the solenoid's electrical health and free movement, and finally the valve body. The vehicle usually still drives, but the harsh shifting stresses the clutch packs and mounts, so it's worth fixing promptly.
Common causes
- Debris or varnish holding the solenoid valve in the applied position
- Dirty or degraded transmission fluid promoting valve sticking
- Mechanically failed or seized pressure control solenoid B
- Worn or contaminated valve body keeping the solenoid from returning
- Electrical fault commanding the solenoid on continuously
- Restricted transmission filter contributing to contamination
- Faulty transmission control module in rare cases
Symptoms
- Check engine light on with P0777 stored
- Harsh, firm, or abrupt shifts
- Delayed engagement into drive or reverse
- Transmission running hotter than normal
- Falling into limp mode in some cases
- Reduced fuel economy when shifts are mistimed
Diagnostic steps
- 1.Check transmission fluid level and condition first — dirty fluid is a leading cause of a sticking solenoid and the cheapest thing to rule out.
- 2.Scan for companion transmission codes; a general P0700 confirms the TCM has stored transmission faults.
- 3.Read line-pressure live data if the transmission supports it, and compare commanded versus actual pressure.
- 4.Inspect the solenoid connector and harness for damage that could be holding the circuit on.
- 5.Resistance-check pressure control solenoid B and, where possible, verify it moves freely rather than sticking.
- 6.If the solenoid tests good, inspect the valve body for varnish, debris, or bore wear keeping the valve applied.
Repair cost
$150 – $900
A transmission fluid and filter service ($150-$350) is the first step and sometimes frees a sticking valve. A pressure control solenoid replacement runs roughly $250-$700 depending on whether it's externally accessible or requires dropping the pan or valve body. Valve-body cleaning or replacement is the higher end. Confirm fluid condition before replacing internal parts.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with transmission shift solenoid replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.