P078B
Shift Timing Solenoid B Range/Performance
Transmission
Generic OBD-II
Medium
What it means
P078B means the shift timing solenoid B isn't performing within its expected range — the transmission's control of when gears engage and disengage is off. The engine still runs and the car drives, but shifts may feel rough or poorly timed. Low or dirty fluid, a worn solenoid, or a sticking valve body are the common causes.
Medium
Can I keep driving? Usually driveable, but shift timing is off — expect rough or poorly-timed gear changes, and get it checked soon to avoid extra transmission wear.
Common symptoms
What you'll notice
- Check-engine light on
- Rough or poorly-timed gear shifts
- Harsh or delayed shifting
- Slipping or flaring between gears
- Reduced fuel economy
Common causes
Most likely first
- Low or dirty transmission fluidLikely
- Faulty shift timing solenoid BCommon
- Sticking or worn valve bodyCommon
- Poor electrical connection or damaged wiring at the solenoidLess often
- Faulty transmission control module (TCM)Less often
How to diagnose & fix
Work through it in order
- Check the transmission fluid level and condition — if it smells burnt or looks dark, service the fluid and inspect the pan for debris.
- Read freeze-frame data and scan for related shift-solenoid codes.
- Inspect the solenoid wiring and connector for damage or corrosion.
- Test the shift timing solenoid B and inspect the valve body for sticking.
- If fluid and electrics are good, verify TCM operation.
FAQ
Quick answers
Is it safe to drive with P078B?+
For short trips, usually yes, but the mistimed shifts add wear and can slip. Address it before the shifting worsens or the transmission overheats.
Can I just clear P078B?+
It will return until the solenoid, fluid, or valve-body issue is fixed. Checking the fluid and the solenoid connector is the cheapest starting point.
Related codes
Often seen with P078B
Read & clear P078B 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