P2686Actuator Supply Voltage C Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- The high case of supply C concerns voltage that should not be there: the rail stays live although the controller has turned it off. Causes are an internal high-side switch that no longer opens or an outside wire touching battery positive. GM's 2023 and 2024 TCM tables run this check during shutdown. With output 7 disabled, a reading above 70 % of battery voltage counts as a shorted switch; the module keeps that finding in permanent memory and reports it once restarted. Battery voltage must stay within 1.5 V during the test, and GM files it as Type B: two failing trips before the lamp lights. Ford lists P2686 as the shorted-switch fault of high side driver 7 in its 2024 TR9070 table and also in the Boss 302S code list. The solenoids can no longer be switched off safely, so a limp mode is likely.
- What you may notice
- MIL after a second trip with the fault
- Limp mode or fixed gear after restart
- Code returns after clearing once the key has been off
- Likely causes
- LikelyInternal high-side switch of the controller stuck conducting
- PossibleSupply wire shorted to a battery-fed circuit in the harness
- RareMoisture in the transmission connector creating a leakage path
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €150 – €1,800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.