Engine-CodesSubaru – P0778 Subaru

P0778 Subaru Code - Pressure Control Solenoid 'B' Electrical

Quick Answer

The P0778 diagnostic trouble code (DTC) for Subaru vehicles specifically refers to an issue with the Pressure Control Solenoid 'B' Electrical circuit. Common causes include Faulty Pressure Control Solenoid 'B', Damaged or corroded wiring harness, Loose or poor electrical connections. 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 Faulty Pressure Control Solenoid 'B', Damaged or corroded wiring harness, Loose or poor electrical connections.
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.
Table of contents Created and updated by William Orellana on Sep 09, 2024
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Code P0778 Subaru Description

The P0778 diagnostic trouble code (DTC) for Subaru vehicles specifically refers to an issue with the Pressure Control Solenoid 'B' Electrical circuit. This solenoid is a vital component of the transmission system, responsible for regulating hydraulic pressure within the transmission. When this solenoid malfunctions or fails to operate correctly, it can lead to various issues with the transmission, affecting the vehicle's overall performance.

OBDII Code P0778 Subaru - Pressure Control Solenoid 'B' Electrical
P0778 Subaru Code - Pressure Control Solenoid 'B' Electrical

Common Causes of P0778 Subaru

  1. Faulty Pressure Control Solenoid 'B'
  2. Damaged or corroded wiring harness
  3. Loose or poor electrical connections
  4. ECM software issues
  5. Transmission fluid contamination or low fluid levels

Symptoms of P0778 Subaru

  1. Harsh shifting between gears
  2. Delayed engagement when shifting into gear
  3. Transmission slipping or jerking
  4. Decreased fuel efficiency
  5. Check engine light illuminated on the dashboard

How to Fix P0778 Subaru

  1. Begin by conducting a thorough diagnosis using a scan tool to confirm the P0778 code.
  2. Inspect the wiring harness and connectors for any signs of damage, corrosion, or loose connections.
  3. Test the Pressure Control Solenoid 'B' for proper operation and replace if necessary.
  4. Clear the DTC using the scan tool and test drive the vehicle to ensure the issue has been resolved.
  5. If the problem persists, further diagnostics may be required to identify any underlying transmission issues.

Cost to Fix P0778 Subaru

The typical repair costs for addressing a P0778 code can vary depending on the specific cause of the issue. In general, replacing a faulty Pressure Control Solenoid 'B' can range from $150 to $300, including parts and labor. However, additional costs may be incurred if further diagnostics or repairs are needed. It's essential to consult with a qualified mechanic or auto repair shop to obtain an accurate estimate based on your vehicle's make and model. Keep in mind that labor rates can fluctuate based on location and the type of repair facility.

Tech Notes for P0778 Subaru

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.

When is the Code Detected?

Engine Control Module (ECM) detectes an open or shorted condition on the solenoid circuit

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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

  • 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

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