P0778Pressure Control Solenoid B Electrical
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Pressure control solenoids are current-controlled proportional valves, and what B and C mean depends on the design: on GM's clutch-to-clutch automatics they are the pressure valves of clutches 2 and 3, on GM's CVT B is primary pulley pressure and C line pressure, on Jatco CVTs B is the secondary pressure valve, on Saab's AF40 B and C are clutch valves SLC1/SLC2. P0778 is the electrical code for valve B. Allison compares current with the duty cycle after 125 ms, after one trip; Mitsubishi's 2009 CVT flags at most 400 mA with 750 mA commanded for 5 s; the 2022 Jatco CVT uses P0778 only for a short to ground; Saab's AF40 flags a deviation between commanded and feedback current of valve SLC1 and keeps only second gear and reverse. Harsh engagement, weak acceleration and no lock-up follow.
- What you may notice
- Harsh engagement jolt
- Weak pulling away and acceleration
- Limp mode (Saab: second and reverse only)
- Check engine light
- Likely causes
- LikelyHarness or connector shorted or open
- LikelyPressure valve B coil faulty – often only replaceable with the valve body
- PossibleTransmission module faulty
- RareSystem voltage
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €150 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.