P0778 Code: Pressure Control Solenoid “B” Electrical

Electronic automatic transmission (AT) vehicles rely on computer-controlled solenoids such as the pressure control solenoid to regulate hydraulic system pressure. This solenoid is also used by the powertrain control module (PCM) to help achieve the correct timing and feel for transmission shifting. If the PCM notices that the pressure control solenoid is not performing as it should, it will log a P0778 code.

What Does the P0778 Code Mean?

Diagnostic trouble code P0778 stands for “Pressure Control Solenoid ‘B’ Electrical.”

The pressure control solenoid determines the position of the pressure regulator valve, which is the part that controls the fluid pressure built up by the pump. Using pulse-width modulation, the pressure control solenoid pushes against an internal valve, opening or closing the hydraulic circuit, depending on the command given by the PCM.

The pressure control solenoid also ensures that the clutch packs in the transmission can provide the necessary gear ratios. An issue with the pressure control solenoid can cause on-board diagnostics (OBD) to log a P0778 code.

Note: The definition of code P0778 might be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P0778 Code?

• Low transmission fluid level
• Faulty pressure control solenoid
• Defective transmission control module
• Internal transmission failure
• Clogged or dirty transmission filter
• Wiring issues (e.g., corroded connector)
• Valve body problems

What are the Common Symptoms of the P0778 Code?

• Slipping transmission
• Illuminated check engine light
• Poor fuel economy
• Vehicle enters limp mode
• Overheating transmission

How to Diagnose the P0778 Code

DTC P0778 is a generic powertrain code that can be logged in vehicles with an OBD-II system. While this might be the case, keep in mind that the steps for diagnosis and repair can vary, depending on vehicle specifications.

If you’re not familiar with the process of diagnosing trouble codes, it might be best to leave the job to the pros. Otherwise, you can go ahead and do it yourself. Here is a video you can watch to get an idea of what the process usually involves.

How to Fix the P0778 Code

Attempting to fix a P0778 code can be tricky without the right tools and technical knowledge. Under these circumstances, it might be best to bring your vehicle to the nearest repair shop and have a trained professional do the job for you. This will ensure that all steps and protocols are followed correctly.

But if you’ve had your fair share of resolving DTCs on your own, then you probably know that there’s no magic bullet that works for all vehicles. So make sure you’re equipped with the right guides before proceeding. Manuals like those from Chilton or an ALLDATA subscription contain vehicle-specific repair information, so you might want to check those out before working on your daily driver.