P0778 Code: Pressure Control Solenoid B Electrical
🟠 Moderate severity · drivable
Drivable, but shifting may be harsh or erratic and continued driving can damage the transmission. Fix it soon.
What P0778 means
There is an electrical fault in the pressure control solenoid B circuit — the computer can't control the solenoid even though the solenoid itself may be mechanically fine. The problem is usually in the wiring, the connector, or the computer's solenoid driver.
Symptoms
- Check engine light on
- Harsh or erratic shifting
- Transmission may be stuck in one gear
- Possible limp mode
Common causes
- most common: Damaged wiring or loose connector at the solenoid
- common: Faulty pressure control solenoid B (internal electrical fault)
- less common: Transmission control module (TCM) driver fault
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Inspect and repair the solenoid wiring and connector | Yes | $10–60 |
| Replace the pressure control solenoid B | Mechanic | $200–500 |
Frequently asked questions
Is an "electrical" code different from a "stuck" code?
Yes. Electrical means the circuit or computer driver is at fault; stuck on/off means the solenoid is mechanically held in one position.
What should I check first?
The wiring and connector at the solenoid — loose or corroded connections are the most common electrical cause.
How much does it cost to fix?
$10–60 for a wiring repair, or $200–500 for a new solenoid.
Related codes
P0775
P0775 Code: Pressure Control Solenoid B Malfunction
P0776P0776 Code: Pressure Control Solenoid B Performance or Stuck Off
P0777P0777 Code: Pressure Control Solenoid B Stuck On
Related guide: The 10 Most Common Check Engine Codes →
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.