P0778
Pressure Control Solenoid B Electrical
Transmission — line pressure control
Generic OBD-II
Medium
What it means
P0778 means the control module has detected an electrical problem — an open or short — in the circuit for pressure control solenoid B. This solenoid helps regulate the transmission's line pressure, so a fault can produce soft, harsh, or slipping shifts and may put the transmission into limp mode. It affects shifting, not whether the engine will start.
Medium
Can I keep driving? Often driveable but the transmission may limp with soft or harsh shifts — drive gently to a shop; it won't stop the engine from starting.
Common symptoms
What you'll notice
- Harsh, soft, or delayed shifting
- Transmission slipping or dropping into limp mode
- Reduced acceleration
- Check-engine light on
Common causes
Most likely first
- Open or short in the pressure control solenoid B circuitLikely
- Failed pressure control solenoid BCommon
- Damaged wiring or corroded connectorCommon
- Loose or corroded electrical connectionsLess often
- Failed transmission control module (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and note any companion transmission codes.
- Inspect the solenoid B wiring and connector for damage, shorts, or corrosion.
- Measure the solenoid's resistance and compare with spec — an open or shorted winding sets this electrical code.
- Repair wiring faults or replace the solenoid as indicated.
- Check transmission fluid level and condition. Clear the code and road-test.
FAQ
Quick answers
Is it safe to drive with P0778?+
You can usually limp to a shop, but expect firm or slipping shifts and possibly limp mode. Don't drive long distances until it's fixed.
Can I just clear P0778?+
Because this is an electrical fault, it typically returns quickly until the circuit or solenoid is repaired.
Related codes
Often seen with P0778
Read & clear P0778 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX