Pressure Control Solenoid B Intermittent
P0779 indicates the transmission control module detected an intermittent electrical signal from the Pressure Control Solenoid B, which regulates hydraulic pressure during gear shifts. This intermittent condition can cause erratic transmission behavior and may trigger limp mode to protect the transmission from damage.
What You Might Notice
- Check Engine Light illuminated
- Transmission enters limp mode or reduced power mode
- Transmission slips or hesitates during gear shifts
- Transmission overheating
- Decreased fuel economy
Most Common Causes
- 1
Defective Pressure Control Solenoid B
The solenoid valve itself may have internal electrical or mechanical failure causing intermittent operation. This is the most common cause of this code.
- 2
Corroded or damaged solenoid connector
Poor electrical connections at the solenoid connector create intermittent signal loss. Corrosion, loose pins, or moisture intrusion are typical issues.
- 3
Faulty or damaged wiring to solenoid
Broken, pinched, or corroded wiring harness between the PCM and solenoid causes intermittent electrical contact problems.
- 4
Dirty transmission fluid or clogged filter
Contaminated fluid reduces solenoid responsiveness and can cause sticking or intermittent operation of the valve spool.
How to Diagnose It
- 1
Check Defective Pressure Control Solenoid B — The solenoid valve itself may have internal electrical or mechanical failure causing intermittent operation. This is the most common cause of this code.
- 2
Check Corroded or damaged solenoid connector — Poor electrical connections at the solenoid connector create intermittent signal loss. Corrosion, loose pins, or moisture intrusion are typical issues.
- 3
Check Faulty or damaged wiring to solenoid — Broken, pinched, or corroded wiring harness between the PCM and solenoid causes intermittent electrical contact problems.
- 4
Check Dirty transmission fluid or clogged filter — Contaminated fluid reduces solenoid responsiveness and can cause sticking or intermittent operation of the valve spool.
How to Fix It
- 1
Inspect and test Pressure Control Solenoid B
Locate the solenoid on the transmission, check for visible damage, test electrical resistance with a multimeter, and verify solenoid operation. Replace if resistance is out of spec or solenoid does not click when energized.
- 2
Inspect solenoid connector and wiring
Disconnect the solenoid connector and inspect for corrosion, loose pins, or moisture. Clean contacts with electrical contact cleaner and apply dielectric grease. Check the entire wiring harness for damage, pinching, or bare wires.
- 3
Change transmission fluid and filter
Drain old transmission fluid, replace the transmission filter and pan gasket, then refill with the correct fluid specification. Dirty fluid can cause solenoid sticking and intermittent faults.
- 4
Check transmission valve body and hydraulic passages
If solenoid tests good and fluid is clean, the valve body may have internal restrictions or sludge blocking proper solenoid movement. Professional transmission service or rebuild may be required.
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