P0778 code meaning
Pressure Control Solenoid B Electrical
Powertrain system Generic code P07xx codes Check engine light
What P0778 means
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.
P0778 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor1 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0778
- Harsh engagement jolt
- Weak pulling away and acceleration
- Limp mode (Saab: second and reverse only)
- Check engine light
Common causes of P0778
- Most likelyHarness or connector shorted or open
- Most likelyPressure valve B coil faulty – often only replaceable with the valve body
- PossibleTransmission module faulty
- Less likelySystem voltage
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Pressure control solenoidTransmission valve bodyTransmission clutchesTransmission control module
What each part of P0778 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 7 | Area: transmission. |
| 78 | The exact fault in that area. |
What to do next
- Note P0778 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0778
What does P0778 mean?
P0778 means "Pressure Control Solenoid B Electrical". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P0778?
Drive gently and only to a workshop. With P0778 the car can go into limp mode (reduced power) to protect itself.
Will P0778 fail an emissions test?
Yes, it can. P0778 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0778 to fix?
Difficulty: medium. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will P0778 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.