OBD-II code · Powertrain (generic)
P078F Transmission Mode Switch C Circuit
General electrical fault on the third transmission mode select switch input C — used for additional drive modes (Sport, Snow, Tow/Haul, Eco) on transmissions that offer more than two operator-selectable shift maps. Without a valid input the TCM falls back to the default mode.
Is it safe to drive with P078F?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyOpen or shorted switch wire
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
- Often, with basic tools
- Typical labour
- 0.3–1.5 h
- Emissions test
- Usually unaffected
- Parts involved
- Transmission Mode Switch C, Wiring Harness
Related codes
- P071ATransmission Mode Switch A Circuit
- P071DTransmission Mode Switch B Circuit
- P07CETransmission Mode Switch D Circuit
- P07D1Transmission Mode Switch E Circuit
- P07D4Transmission Mode Switch F Circuit
- P078CShift Timing Solenoid B Low
- P078DShift Timing Solenoid B High
- P078EShift Timing Solenoid B Intermittent
- P0790Normal/Performance Switch Circuit
- P0791Intermediate Shaft Speed Sensor A Circuit
- P0792Intermediate Shaft Speed Sensor A Circuit Range/Performance
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.