P0779 Fault Code in Ford: Causes, Symptoms, and Fixes

The Transmission Control Module (TCM) detected that Pressure Control Solenoid B is working inconsistently (not holding stable pressure). Unlike P0778 (electrical fault), P0779 points to intermittent operation — sometimes working, sometimes failing.

Common Symptoms:

1. Intermittent harsh or delayed shifts
2. Gear slipping (sometimes fine, sometimes rough)
3. Transmission may go into fail-safe/limp mode
4. Check Engine Light (CEL) comes and goes
5. Possible overheating if driven for long with this issue

Possible Causes:

1. Intermittent solenoid B failure (sticking, worn, or weak coil)
2. Loose or corroded wiring/connectors to the solenoid
3. Low or dirty transmission fluid causing sticking valves
4. Internal hydraulic issues (valve body problems)
5. Faulty TCM (less common)

Recommended Fix:

1. Check fluid – level, quality, contamination.
2. Inspect wiring/connector for loose pins, corrosion, or intermittent contact.
3. Bench test solenoid B – resistance should be within spec (if it fluctuates, replace).
4. If wiring and solenoid are fine → check valve body for sticking valves.
5. Reprogram or replace TCM if no mechanical/electrical faults found.