OBD-II code · Powertrain (generic)
P078D Shift Timing Solenoid B High
Shift timing solenoid B control circuit reads stuck high — short to battery voltage or open coil.
Is it safe to drive with P078D?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyControl wire shorted to battery voltage
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.8–3 h
- Emissions test
- Usually unaffected
- Parts involved
- Shift Timing Solenoid B, Tcm
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.