P0778 OBD-II Trouble Code: Pressure Control Solenoid B Electrical

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Cost of diagnosing the P0778 code

P0778 is a diagnostic trouble code (DTC) for "Pressure Control Solenoid B Electrical". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic for $154.99 . Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $50.0 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate* Credit towards follow-up repair Earliest Availability
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Toyota $154.99 $50.0
BMW $164.99 $50.0

*Estimates may vary by market

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P0778 code definition

The PCM stores the P0778 code when an abnormal voltage reading is detected from the electronic pressure control solenoid, or the correlating circuit.

What the P0778 code means

In order to operate the engine efficiently, the PCM monitors the fluid pressure from a variety of sensors within the engine. For every specific driving condition, there is a preset manufacturer specification that tells the PCM what the voltage reading should be to ensure optimal fluid pressure. If the pressure control solenoid does not report the proper voltage reading, the PCM assumes a problem with the engine fluid pressure, and stores the P0778 code.

What causes the P0778 code?

Common causes may include:

  • Faulty electronic pressure control solenoid B, or solenoid B valve
  • Blocked transmission fluid passages
  • Internal transmission failures
  • Low transmission fluid, or dirty or contaminated transmission fluid
  • Faulty electrical components within the pressure control solenoid B

What are the symptoms of the P0778 code?

The symptoms that can accompany the P0778 code can vary greatly. In addition to the illuminated Check Engine lamp, drivers may observe:

  • Inability to shift gears
  • Harsh shifting
  • Slipping transmission
  • Overheated transmission
  • Decreased fuel economy
  • Failure of the torque converter clutch to either engage or disengage

In addition, there may be other torque converter clutch, gear ratio, lock up, shift solenoid, or transmission slippage codes stored with the P0778 code.

How does a mechanic diagnose the P0778 code?

After an OBD-II scanner detects the P0778 code, there are two things that the technician should turn to first: a visual inspection of all electrical wiring, connectors, and harnesses, and a visual inspection of the transmission fluid. Any damaged or loose electrical components should be replaced; contaminated transmission fluid should be flushed, and the system should be refilled with clean fluid.

These are two very common and relatively inexpensive repairs that can cause this code. After these, and each subsequent repair, the mechanic should clear the PCM and retest the system. If the P0778 code returns, then the mechanic should begin testing the solenoid and other potentially faulty components, until the fault is found.

Common mistakes when diagnosing the P0778 code

The most common mistake made during the diagnostic process for the P0778 code is replacing the high pressure pump, rather than checking for faulty solenoids or wiring.

How serious is the P0778 code?

The P0778 code represents a serious drivability issue. Without the ability to monitor and actuate changes within the engine fluid pressure, the vehicle may not operate safely or optimally. It is important to have this repair done as soon as possible after detecting this code.

What repairs can fix the P0778 code?

Common repairs may include:

  • Replacing a faulty electronic pressure control solenoid B, or solenoid B valve.
  • Clearing and refilling blocked transmission fluid passages.
  • Addressing any internal transmission failures.
  • Refilling low transmission fluid, or replacing dirty or contaminated transmission fluid.
  • Repairing or replacing any faulty electrical components within the pressure control solenoid B.

Need help with a P0778 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

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