P0777🔧 Transmission / Hydraulic pressure controlStop and fix promptly

P0777: Pressure Control Solenoid B Stuck On (Meaning, Causes, Fixes)

Reviewed 2026-10-25 · Based on 2 cited source(s)

What P0777 means

An automatic transmission changes gears by applying clutches and bands with fluid pressure. The control module uses pressure control solenoids to set that pressure in each hydraulic circuit at the right moment. OBD-Codes.com says the powertrain control module (PCM) sets P0777 when pressure control solenoid B is stuck in the on position. RepairPal defines P0777 as Pressure Control Solenoid "B" Stuck On, but its explanation only says the transmission control module (TCM) sets it when a pressure control solenoid is not performing as desired. P0777 belongs to the B solenoid family: P0775 (general malfunction), P0776 (performance or stuck off), P0777 (stuck on), P0778 (electrical) and P0779 (intermittent) (OBD-Codes.com, RepairPal). It is a generic OBD-II code that OBD-Codes.com says shows up on Ford, Lincoln, Mercury, Jaguar, Chevrolet, Toyota, Nissan, Allison/Duramax, Dodge, Jeep, Honda, Acura and other vehicles, but the exact test values and repair steps vary by transmission, so the vehicle's service information should come first.

Severity: can I keep driving?

Stop and fix promptly

Get it checked soon. RepairPal rates P0777 Urgent, meaning it can cause severe damage or be unsafe. OBD-Codes.com calls it moderate at first but says it can get worse quickly if it isn't fixed. The transmission may slip, overheat, catch in gear or drop into limp mode, so avoid hard acceleration, towing and long trips until it's diagnosed, and get off the road safely if it suddenly loses drive.

Common symptoms

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

  1. Failed pressure control solenoid (both sources)
  2. Low transmission fluid (RepairPal), or dirty or contaminated fluid (OBD-Codes.com)
  3. Dirty or clogged transmission filter (OBD-Codes.com)
  4. Wiring problem, or a corroded or damaged connector (both sources)
  5. Faulty transmission control module (RepairPal) or PCM (OBD-Codes.com)
  6. Defective transmission pump, defective valve body or restricted hydraulic passages (OBD-Codes.com)
  7. The sources differ: RepairPal lists only the module, low fluid, the solenoid and wiring, while OBD-Codes.com adds fluid contamination, the filter, the pump, the valve body and blocked passages. They also disagree on severity, with RepairPal rating it Urgent and OBD-Codes.com calling it moderate at first, they name different computers (TCM versus PCM) as the one that sets the code, and only OBD-Codes.com explains the stuck-on condition itself

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

  1. Read all stored codes and freeze frame data before clearing anything; other B solenoid codes (P0775 to P0779) or other transmission codes can point to the real cause.
  2. Check for technical service bulletins (TSBs) for your vehicle, year and transmission; OBD-Codes.com says this can save a lot of time.
  3. Check the transmission fluid level and condition using the procedure in your owner's or service manual, and look for burnt smell, dark color or debris.
  4. Check your records for when the fluid and filter were last changed (OBD-Codes.com).
  5. Inspect the wiring and connectors to the transmission pressure control solenoids, the pump (if electric) and the computer for damage, corrosion, loose connections or damaged pins.
  6. Further testing needs a digital multimeter and your vehicle's specific voltage and pressure specs; OBD-Codes.com says wiring should normally read 0 ohms with the power off unless the service data says otherwise.

Typical fixes

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

  • The transmission is slipping, overheating or stuck in limp mode
  • The fluid is burnt or full of debris
  • The fluid level and wiring check out and the code comes back
  • Testing needs pressure gauges, a scan tool or removing the pan and valve body
  • OBD-Codes.com warns this code can be misdiagnosed as an engine misfire, a transmission pump problem, an internal transmission problem or a driveline problem, so a proper diagnosis matters before buying parts

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Is P0777 serious?

Treat it as serious. RepairPal rates it Urgent. OBD-Codes.com says it usually starts as moderate but can get worse quickly, with slipping, overheating, catching in gear and limp mode possible.

What's the difference between P0776 and P0777?

Both point at pressure control solenoid B. P0776 means its performance is off or it is stuck off, while P0777 means it is stuck on (OBD-Codes.com, RepairPal).

Can low transmission fluid cause P0777?

Yes. RepairPal lists low fluid as a common cause, and OBD-Codes.com lists dirty or contaminated fluid and a clogged filter, so checking the fluid is the first step.

How much does it cost to fix P0777?

Neither source gives a repair cost. It can range from a fluid service or wiring repair to a new solenoid, valve body or control module, so get a diagnosis and a written estimate first.

Sources

  1. OBD-Codes.com: P0777 Pressure Control Solenoid B Stuck On (John Ingalls)
  2. RepairPal: P0777 Pressure Control Solenoid "B" Stuck On (rated Urgent)

Last reviewed 2026-10-25. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.