P078F is the circuit fault of a third transmission mode switch (C), after A (P071A–P071C) and B (P071D–P071F): its state is invalid or implausible. GM's transmission modules of 2023 and 2025 list the number only as a blocking condition for another check, without a description of their own; GM reports its drive mode selector today under P05D0–P05D3 (8-step resistor ladder, two trips). No manufacturer document available to us describes P078F itself. The mode then cannot be selected and the transmission stays on its normal schedule.
Medium severity. Can I keep driving?Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
Symptoms
- Drive mode (sport, winter, tow) cannot be selected
- Mode indicator missing
- Transmission stays on the normal program
Most likely causes
- Switch or button faulty or sticking
- Wire or connector open or shorted
- Moisture or dirt in the centre console
- Control module
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: easy
What each character of P078F means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 7: Transmission
- 8F: Specific fault in that system
Frequently asked questions
Can I keep driving with code P078F?
Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
What causes code P078F?
The most common causes are: switch or button faulty or sticking; wire or connector open or shorted; moisture or dirt in the centre console.
Related codes
- P071ATransmission Mode Switch A Circuit
- P071DTransmission Mode Switch B Circuit
- P0790Normal/Performance Switch Circuit
- P05D0Driver Mode Select Switch A Circuit
- P05D1Driver Mode Select Switch A Circuit Low
- P05D2Driver Mode Select Switch A Circuit High
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.