P0778: Pressure Control Solenoid ‘B’ Electrical DTC Trouble Code

The pressure control solenoid is responsible for maintaining the fluid pressure needed to shift gears. If the ECU detects an electrical problem with one of the pressure control solenoids, it will trigger a P0778 diagnostic trouble code.

Need a replacement transmission? Get an estimate for replacement transmissions and local installation. Look up your transmission model by vehicle make and model.

What Transmission Do I Have?

How Serious is the Code?

If your vehicle has a P0778 DTC, it likely means the ECU can’t control a particular solenoid, which can cause serious drivability and safety concerns.

Symptoms

Symptoms of a P0778 include:

  • Check engine light
  • Harsh, erratic shifts
  • Slipping
  • Engine stalls while stopped in gear
  • Vehicle won’t move when in gear
  • Increased fuel consumption
  • Transmission overheats
  • Limp mode

Causes

  • Insufficient transmission fluid
  • Dirty transmission fluid / filter
  • Frayed wiring / damaged connectors
  • Failing pressure control solenoid
  • Failing transmission pump
  • Internal pressure problems
  • Valve body issue
  • ECU or TCM failure

How to Diagnose the Code?

If the transmission fluid is full of dirt, sludge or any metallic bits, then the pressure control solenoids might not be able to function properly. The presence of metal fragments can also indicate internal component failure, so checking the ATF condition should be the first step in diagnosing a pressure control solenoid DTC. If the fluid is dirty and pressure blockages are suspected, then a transmission flush may be performed to restore hydraulic pressure.

If there are no issues with the transmission fluid, then the wiring and connectors should be checked for signs of damage, corrosion and/or a short. If everything appears fine, then the pressure control solenoid will need to be tested according to the manufacturer’s procedure. If no issues have been found by this point, then the problem could lie with the torque convertor, transmission pump, valve body, or pressure regulator.

Common Mistakes When Diagnosing

It’s not uncommon for many mechanics to blame the transmission pump for this DTC, when it could actually be a wiring problem, or a faulty pressure control solenoid.

What Repairs Will Fix P0778?

  • Changing the fluid and filter
  • Replace faulty pressure control solenoid
  • Repair or replace a faulty transmission pump
  • Repair or replace defective transmission valve body
  • Transmission flush to clean passages
  • Cleaning corrosion from connectors
  • Repairing or replacing wiring
  • Flashing or replacing PCM

Related Codes

P0775 – Pressure Control Solenoid ‘B’

P0776 – Pressure Control Solenoid ‘B’ Performance or Stuck Off

P0777 – Pressure Control Solenoid ‘B’ Stuck On

P0779 – Pressure Control Solenoid ‘B’ Intermittent

Need a replacement transmission? Get an estimate for replacement transmissions and local installation. Look up your transmission model by vehicle make and model.

What Transmission Do I Have?

Full Transmission DTC Codes Table

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Ali
2 years ago

Code P0788

FrankO
6 years ago

my mechanic performed resistance test on pressure control selonoid B and said it passed at a cost of $380.00 but 2 days later I felt the trans sort of lurch or down shift and then the check engine light came back on. I had the code checked and it was for the same problem.Po778. Help!

Frank
6 years ago

Po778 is the code my Ford fusion is displaying. Does an anyone have an idea how much this typically costs to repair?

FrankO
6 years ago
Reply to  Frank

It cost me $380.00, but I am still having the same problem.

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