P0778 - PRESSURE CONTROL SOLENOID "B" ELECTRICAL

Automatic transmissions rely on varying degrees of hydraulic pressure to shift gears and engage transmission components such as clutches and belts. To make these shifts efficient, the vehicle’s computer uses pressure control solenoids to direct transmission fluid from one hydraulic circuit to another.

For automatic transmissions to achieve an efficient process for setting gear ratios, the fluid must be channeled precisely. If a pressure control solenoid fails, the fluid cannot be effectively controlled. If the Powertrain Control Module (PCM) detects that the output voltage of the pressure control solenoid “B” is problematic or out of range, it will set DTC P0778 OBDII.

• Check Engine light is on.
• Gear changes are hard.
• Transmission slipping and overheating.
• Poor fuel economy.
• Other transmission-related fault codes are stored.
• The car goes into emergency mode.
• The gearbox slips when shifting gears.

The factors for which the P0778 OBD2 diagnostic code is stored are:

• Perhaps the system has bad wiring or connectors.
• Pressure control solenoid "B" may be faulty.
• The transmission fluid could be contaminated or excessively low.
• The valve body may be damaged.

The steps to fix the P0778 OBDII fault code are:

• Consult your vehicle's service manual for information on the location of the pressure control solenoid "B" and its wiring. Then inspect them for damage such as wear, burning, or corrosion. Repair or replace any wires that require repair or replacement.
• Perform resistance, continuity, ground, and reference voltage tests on all wiring connected to the solenoid. All values obtained must be within the manufacturer's specifications. Repair it as applicable.
• Verify that the transmission fluid has a level necessary for proper operation and that it is not dirty or contaminated. Replace it if required.
• Test the internal resistance of the solenoid, taking as reference the steps indicated in the user's manual. If the internal resistance of the solenoid is not as specified by the manufacturer, it must be replaced.