P078D
Shift Timing Solenoid B High
Transmission — shift control
Generic OBD-II
Medium
What it means
P078D means the control circuit for shift timing solenoid B is reading high, usually an open or high-voltage electrical fault. This solenoid helps time gear engagement, so a fault can make shifts rough or poorly timed. The engine still starts and runs; the problem is in the solenoid or its wiring rather than a no-start condition.
Medium
Can I keep driving? The car still drives, but shifts may be rough or poorly timed — get it checked before long trips.
Common symptoms
What you'll notice
- Check-engine light on
- Rough or poorly timed gear shifting
- Harsh or delayed shifts
Common causes
Most likely first
- Faulty shift timing solenoid BLikely
- Open or high-resistance wiring or connector in the circuitCommon
- Poor electrical connection at the solenoidCommon
- Low or contaminated transmission fluidLess often
- Failed transmission control module (TCM) — least commonLess often
How to diagnose & fix
Work through it in order
- Confirm the code and read freeze-frame data.
- Inspect the solenoid wiring and connector for opens or corrosion — a high reading usually means an open circuit.
- Measure the solenoid resistance against spec.
- Replace the solenoid if faulty; check the fluid condition.
- Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P078D?+
Short trips are usually okay, but repeated rough shifting stresses the transmission — have it repaired soon.
Can I just clear P078D?+
It returns until the solenoid or circuit fault is repaired.
Related codes
Often seen with P078D
Read & clear P078D 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