P2685 means the third actuator supply rail sags while it is switched on, almost always because the line or one of the loads it feeds has a path to ground. Unlike the open and switch faults of this rail, GM's 2023 and 2024 TCM tables check this one continuously during operation: if the voltage at high-side output 7 falls below a share of the supply, or the averaged output current runs too high, a timer counts up and the fault is confirmed after 60 ms. Battery voltage must lie between 8.75 and 18 V, the engine must not be cranking, and the test is suspended when P0882 or P0883 is present; GM rates it Type A. Ford's 2024 summary lists P2685 as the shorted-load fault of high side driver 7 in the TR9070 dual-clutch unit. The protected output switches off and the transmission falls back to a failsafe mode.
Medium severity. Can I keep driving?If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
Symptoms
- MIL on during the same trip
- Failsafe gear, no normal shifting
- Blown fuse possible on the transmission supply
Most likely causes
- Supply wire chafed through and touching ground
- Shorted solenoid coil on this rail drawing excess current
- Weak battery or charging fault pulling the whole supply down
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It can trigger limp mode.
- It affects emissions.
What each character of P2685 means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 6: Control modules and outputs
- 85: Specific fault in that system
Frequently asked questions
Can I keep driving with code P2685?
If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
What causes code P2685?
The most common causes are: supply wire chafed through and touching ground; shorted solenoid coil on this rail drawing excess current; weak battery or charging fault pulling the whole supply down.
Related codes
- P2684Actuator Supply Voltage C Circuit/Open
- P2686Actuator Supply Voltage C Circuit High
- P2670Actuator Supply Voltage B Circuit Low
- P0658Actuator Supply Voltage A Circuit Low
- P26E8Actuator Supply Voltage D Circuit Low
- P0882TCM Power Input Signal Low
Sources
- gsi.ext.gm.com: 23OBDG07
- gsi.ext.gm.com: 24OBDG07
- fordservicecontent.com: OBDSM2400OUTPUT 16Jul2024 WSM final V2 MCS7001
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.