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P0779 — Pressure Control Solenoid B Intermittent

Generic OBD-II · all makesPowertrain (engine & transmission)

Code P0779 indicates that the powertrain control module has detected an intermittent electrical or performance fault in the Pressure Control Solenoid B circuit. This solenoid regulates transmission line pressure based on commands from the control module. An intermittent fault means the problem comes and goes rather than being constant.

Symptoms

What causes it — most likely first

1. Wiring or connector issue

Corroded, loose, or chafed wiring and connectors in the solenoid circuit are the most common cause of intermittent solenoid codes. Heat and vibration near the transmission accelerate these failures.

2. Pressure control solenoid B failing

The solenoid itself may be electrically intermittent due to internal wear, coil degradation, or contamination. It can test fine at rest but fail when hot or under load.

3. Contaminated or degraded transmission fluid

Dirty fluid with clutch material or metal debris can cause solenoids to stick intermittently and can also degrade internal solenoid components over time.

4. Internal transmission hydraulic issue

A sticking valve, blocked passage, or worn pressure regulator can cause line pressure fluctuations that the control module interprets as a solenoid circuit problem.

5. Powertrain control module fault

A failed driver circuit inside the PCM is rare but possible. This should only be considered after all wiring, solenoid, and hydraulic causes have been thoroughly ruled out.

How it's diagnosed

  1. Scan all codes and record freeze frame data to identify conditions when the fault occurs.
  2. Visually inspect the transmission wiring harness and connectors for corrosion, damage, or loose pins.
  3. Perform a wiggle test on the solenoid wiring while monitoring solenoid B data on a scan tool to check for intermittent signal dropouts.
  4. Check transmission fluid level and condition; look for contamination or burnt smell.
  5. Test pressure control solenoid B resistance and compare to specification, then repeat the test when the transmission is at operating temperature.
  6. If wiring and solenoid test good, perform a line pressure test to evaluate internal hydraulic health before considering control module diagnosis.

Code facts & related codes

SystemPowertrain (engine & transmission)
StandardizationSAE generic — identical on every make
Related codesP0770 — Shift Solenoid EP0771 — Shift Solenoid E Performancestuck OffP0772 — Shift Solenoid E StuckP0773 — Shift Solenoid E ElectricalP0774 — Shift Solenoid E IntermittentP0775 — Pressure Control Solenoid B

Frequently asked

Can I drive with a P0779 code?

Short distances may be possible, but continued driving risks transmission damage from improper line pressure. Harsh or soft shifting can accelerate clutch wear and lead to more expensive internal damage.

Does P0779 mean I need a new transmission?

No. Many cases are resolved by repairing wiring, replacing a single solenoid, or servicing the fluid. Internal transmission failure is possible but is not the most common cause of this code.

Should I replace the PCM if I have a P0779 code?

Almost never. PCM driver failure is rare for this code. Most shops and technicians incorrectly blame the PCM when they have not fully diagnosed the wiring, connector, or solenoid. Replacing the PCM without confirming all other causes is a waste of money.

Why does the code come and go?

Intermittent faults are typically caused by wiring that loses connection under vibration or heat, or by a solenoid that fails only when hot. The control module sets the code only when it detects the fault during a drive cycle.