P2685: Actuator Supply Voltage C Circuit Low
What to do
Expect several warning lights and reduced power, possibly intermittent rather than constant.
As with the other supply codes, do not let a list of unrelated parts be replaced. A shared supply has failed and everything on it is reporting a fault.
Ask for one specific thing, because it is quick and it narrows the search a lot: are the other actuator supply circuits affected too? If all of them are down, the fault is in what they share — the relay, the main feed, or an earth connection. If only this one is, it is either that circuit's own wiring or a single faulty part on it dragging the supply down. That distinction decides where the time goes.
Also mention when it happens — under load, on a hill, with the air conditioning on. A supply that only fails when several things draw current at once is a weak connection rather than a dead short, and needs voltage-drop testing while it is working rather than a continuity check at rest.
What this code means
The third actuator supply rail reads below its valid range — a short to ground, or a supply collapsing under load.
The rail concept is explained at P2669, and the distinction between a rail that is shorted and one that is merely sagging — which leads to different repairs, and which is found by voltage-drop testing under load rather than by a static measurement — is set out at P2670. Both apply here unchanged.
The one thing worth adding is a check that becomes available precisely because there are three rails, and it is quick. The rails share a feed path — the same relay, the same main supply, the same ground points — before they separate inside the module. So which rails are affected localises the fault immediately.
- All three rails low points at what they share: the relay, the main feed, or the module's ground. It is almost never three separate failures.
- One rail low while the others are healthy points past the shared supply to that rail's own circuit — or to a single actuator on it that has shorted internally and is dragging its own rail down.
That comparison costs nothing but reading the stored codes properly, and it decides whether the next hour is spent on a ground strap or on disconnecting actuators one at a time.
Likely causes
Start here
- Wiring shorted to ground · moderate
- High resistance in the module supply · moderate
- Poor module ground connection · moderate
- Faulty module power relay · moderate
Less common
- Damaged module supply wiring · moderate
- Shorted injector dragging the driver down · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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