Fix P0777: Mechanic’s solutions that WORKED

The P0777: Pressure Control Solenoid B Stuck On code indicates that the Pressure Control Solenoid B within the transmission is stuck in the “on” position. This solenoid is crucial for managing the hydraulic pressure that activates the transmission’s gears and clutches. When stuck on, it can disrupt the normal operation of the transmission, leading to noticeable symptoms like slipping gears or failure to shift properly.

P0777 quick overview

Meaning	P0777: Pressure Control Solenoid B Stuck On
Is it serious?	Yes, this code is serious as it can lead to transmission issues including slipping, delayed shifting, or even complete failure to engage gears, affecting vehicle performance and safety.
Possible causes	– Faulty pressure control solenoid B – Dirty or contaminated transmission fluid – Clogged transmission filter – Wiring or electrical problems affecting the solenoid – Hydraulic blockages within the transmission – Transmission control module (TCM) software needing updates
How to diagnose?	Check Transmission Fluid: Verify the level and condition of the transmission fluid. Inspect Solenoid and Wiring: Look for damage or disconnections in the solenoid’s wiring and connectors. Replace Solenoid: If diagnostics confirm failure, replace the pressure control solenoid B. Flush Transmission Fluid: Change the transmission fluid and filter if contaminated. Conduct Hydraulic Pressure Test: To identify any hydraulic issues within the transmission. Update TCM Software: Check for TCM updates that might address the issue. Clear Adaptive Learning: Reset the transmission’s adaptive learning and perform a road test.

How to fix P0777 – learn from mechanics

I looked into P0777 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Dodge

Vehicle Information: 2007 Dodge Caliber SXT 2.0L Transmission

Issue + Repair History:

• Vehicle purchased at auction with a known bad transmission.
• No prior repair history as the vehicle was acquired with the issue.

Other Test Results:

• Checked codes revealed P0842 (Transmission Fluid Pressure Sensor/Switch “A” Circuit Low) and P0777 (Pressure Control Solenoid “B” Stuck On).
• Driving symptoms included a noisy transmission and rattle/vibration at startup and slowdown.

Suggestions to Fix Issue:

• The TCM does require a learning procedure to be performed after installation.
• Transfer the ROM (Read-Only Memory) module from the original transmission to avoid reprogramming.
• Snap-on scan tools may initialize the TCM without the need for dealership reprogramming.
• Valve bodies, speed sensors, park neutral switches, or complete transmissions are the only parts available from manufacturers.
• Aftermarket parts are available for rebuilding CVTs.

Final Fix:

• Ended up reprogramming the TCM and updating software with the help of a factory-trained technician.
• After addressing the reprogramming and updates, the vehicle operated correctly.

Case #2: Jeep

Vehicle Information: 2010 Jeep Patriot Sport 2.4L

Issue + Repair History:

• Transmission slips when hot, particularly after 70 miles of driving with the last 25 being hilly.
• Trans temp light and CEL come on, setting 3 pending codes.
• Owner’s manual suggestion followed; vehicle functioned normally after cooling.
• Fluid full and appears clean.

Other Test Results:

• Codes: P0700, P0741, P0777 – all pending.
• Trans temp did not exceed 170°F in a 20-mile test drive.

Suggestions to Fix Issue:

• Drop the pan to check for debris; if clean, proceed with a fluid and filter change using OEM CVT fluid.
• Inspect the thermostat block in the cooler lines for blockage and replace if necessary.
• Verify cooler flow; replace as needed.
• Consider the vehicle’s mileage may indicate end-of-life for CVT, but try fluid change first.
• Check for a thermostat or cooler blockage contributing to overheating.

Final Fix:

• Changing the transmission fluid and strainer resolved the issue after a 2-hour test drive.
• Fresh fluid critical for TCC function; CVT transmissions may not show fluid color change as traditional automatics do.
• Maintenance questions arose regarding fluid change intervals and the importance of fresh fluid for CVT function.

Case #3: Toyota

Vehicle Information: 2012 Toyota Camry SE 2.5L

Issue + Repair History:

• MIL illuminated with code P0777.
• Customer reports delayed shifting and occasional jerking motion during acceleration.
• Vehicle has a history of regular maintenance, but transmission fluid was not changed at recommended intervals.

Suggestions to Fix Issue:

• Perform a comprehensive diagnostic scan to confirm the P0777 code and check for additional codes.
• Inspect the transmission fluid level and quality; replace if old or contaminated.
• Test the pressure control solenoid B for electrical failure or mechanical sticking.
• Clear the transmission adaptive learning and perform a road test to recalibrate shifting patterns.

Final Fix:

• Replacing the pressure control solenoid B and changing the transmission fluid and filter resolved the issue. The vehicle’s shifting performance improved significantly after the solenoid replacement and transmission fluid service.

Case #4: Nissan

Vehicle Information: 2015 Nissan Altima S 2.5L

Issue + Repair History:

• Intermittent P0777 code triggered with no noticeable driving issues initially.
• Over time, the vehicle began experiencing hard shifts and occasionally would not shift out of lower gears.
• Transmission serviced approximately 20,000 miles ago with no issues reported until now.

Suggestions to Fix Issue:

• Inspect the wiring and connectors leading to the pressure control solenoid B for any signs of wear or damage.
• Perform an ohm test on the solenoid to ensure it falls within factory specifications.
• Check the transmission control module (TCM) for software updates that may address known shifting issues.

Final Fix:

• A frayed wire harness to the pressure control solenoid B was identified and repaired. Additionally, a TCM software update was performed. These actions cleared the P0777 code, and the transmission returned to normal operation.

Case #5: Chevrolet

Vehicle Information: 2009 Chevrolet Malibu LT 2.4L

Issue + Repair History:

• P0777 code present with transmission slipping and failing to engage gears properly.
• Several attempts to clear the code were unsuccessful, and symptoms persisted.
• No recent transmission maintenance or repairs prior to the onset of symptoms.

Suggestions to Fix Issue:

• Perform a hydraulic pressure test to check for issues within the transmission that could cause solenoid malfunction.
• Inspect the internal transmission components for any signs of wear or damage that could contribute to the solenoid sticking.
• Replace the transmission fluid and filter as preventative maintenance.

Final Fix:

• The hydraulic pressure test revealed internal transmission wear contributing to the solenoid’s failure to operate correctly. Pressure control solenoid B was replaced, and worn internal components were repaired. After these repairs, the transmission operated smoothly, and the P0777 code did not return.

Advice	Brief Description of Diagnostic Step
Inspect the transmission fluid	Check the transmission fluid level and condition; replace if old or contaminated to ensure proper hydraulic pressure and lubrication.
Replace the pressure control solenoid B	If diagnostics confirm solenoid failure, replace the solenoid responsible for controlling hydraulic pressure to the transmission’s clutches and bands.
Check wiring and connectors	Inspect the electrical wiring and connectors leading to the solenoid for signs of wear, damage, or corrosion that could interrupt the solenoid’s operation.
Perform a hydraulic pressure test	Conduct a hydraulic pressure test to identify any issues within the transmission that could affect solenoid performance.
Clear the transmission adaptive learning	After repairs, clear the transmission’s adaptive learning and perform a road test to recalibrate shifting patterns.
Inspect internal transmission components	Check internal components for wear or damage that could contribute to the solenoid’s malfunction, especially if the hydraulic pressure test indicates problems.
Update Transmission Control Module (TCM) software	Check for and apply any available software updates for the TCM that may address or improve shifting issues related to the solenoid’s function.
Replace transmission fluid and filter	As preventive maintenance or part of the repair process, replace the transmission fluid and filter to remove contaminants and ensure proper operation.