AutoCodes – Subaru – P0778 Subaru

P0778 Subaru Code - Pressure Control Solenoid 'B' Electrical

Quick Answer

The Pressure Control (PC) Solenoid Valve an electronic pressure regulator that controls transmission line pressure based on current flow through its coil windings. Common causes include Low transmission fluid level, Dirty transmission fluid, Faulty line pressure solenoid 'B' valve. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P0778 Subaru indicates Pressure Control Solenoid 'B' Electrical.
Common causes: Common causes include Low transmission fluid level, Dirty transmission fluid, Faulty line pressure solenoid 'B' valve.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 21,368

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jan 30, 2019

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0778 Subaru Description

The Pressure Control (PC) Solenoid Valve an electronic pressure regulator that controls transmission line pressure based on current flow through its coil windings. As current flow is increased, the magnetic field produced by the coil moves the solenoid’s plunger further away from the exhaust port. Opening the exhaust port decreases the output fluid pressure regulated by the PC solenoid valve, which ultimately decreases line pressure. The line pressure solenoid valve regulates the oil pump discharge pressure to suit the driving condition in response to a signal sent from the Transmission Control Module (TCM).

OBDII Code P0778 Subaru - Pressure Control Solenoid 'B' Electrical - AutoCodes.com — P0778 Subaru Code - Pressure Control Solenoid 'B' Electrical

What does this mean?

What are the Possible Causes of the DTC P0778 Subaru?

Low transmission fluid level
Dirty transmission fluid
Faulty line pressure solenoid 'B' valve
Line pressure solenoid 'B' valve harness is open or shorted
Line pressure solenoid 'B' valve circuit poor electrical connection

How to Fix the DTC P0778 Subaru?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

When a transmission solenoid is malfunctioned, in most cases the problem is not the electrical part of the solenoid; the problem is foreign material obstructing the mechanical function of the solenoid or the flow of the fluid through the transmission valve body. If the transmission fluid is dirty, it's recommended to change the transmission fluid and if possible removing the transmission pan for further diagnosis. Excessive debris or metal particles on the transmission pan could be an indication that there is a mechanical transmission failure and that the transmission will need to be rebuilt or replaced.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0778 Subaru code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0778 Subaru Code

What does OBDII code P0778 mean for a Subaru?

Code P0778 indicates an electrical issue with the Pressure Control Solenoid 'B,' which helps regulate transmission fluid pressure for smooth gear shifts.

What are the common symptoms of code P0778 in a Subaru?

Symptoms may include transmission slipping, harsh or delayed shifting, poor fuel efficiency, and activation of the check engine light.

What causes code P0778 in a Subaru?

Causes can include a faulty pressure control solenoid, damaged wiring or connectors, low transmission fluid levels, or a malfunctioning transmission control module (TCM).

Can driving with code P0778 damage my Subaru?

Yes, prolonged driving with this code can cause transmission damage and further issues due to improper fluid pressure regulation.

How do I diagnose code P0778 in a Subaru?

Diagnosis involves inspecting the solenoid, checking wiring and connectors for damage or corrosion, and testing transmission fluid levels and quality.

How do I fix code P0778 on a Subaru?

Repairs may involve replacing the pressure control solenoid, repairing damaged wiring or connectors, refilling or flushing transmission fluid, or replacing the TCM.

Can low transmission fluid cause code P0778 in a Subaru?

Yes, insufficient or degraded transmission fluid can disrupt pressure regulation and trigger this code.

How much does it cost to fix code P0778 on a Subaru?

Repair costs vary but typically range from $200 to $500 for solenoid replacement; additional costs may arise if wiring or the TCM needs repairs.

Is code P0778 common in Subaru vehicles?

This code can occur in Subaru vehicles, especially if the transmission is not properly maintained or has high mileage.

Can I clear code P0778 without fixing the problem?

Clearing the code without addressing the underlying issue will only temporarily remove the warning, and the problem will likely return.

Discuss the causes and fixes for P0778 Subaru OBDII Code

Submit a New Comment

todd
Date: October 1, 2017 at 9:32 pm

I hit something on the road. my at light is blinking fast. there is a small dent in the trans oil pan the trans is in one gear maybe 3rd

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OBDIITech
Date: October 2, 2017 at 1:16 am

You have to remove the transmission pan to check for damage. You may have damage the transmission valve body.

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