U0085: Vehicle Communication Bus F (-) Open
What to do
Expect equipment on the converted part of the vehicle to have stopped working. Everything at U0082 applies — including the free test: does the fault change as the vehicle is loaded, or as the body is moved?
Two things are worth asking for when the break is found.
Ask for the second wire to be inspected along the same stretch. On a working vehicle the damage is usually mechanical — a strap, a load, a stone, or a flex point — rather than slow corrosion, and whatever crushed or cut one wire almost certainly reached the other. A vehicle that earns its living cannot afford to come back for the second half.
And if the break is where the wiring flexes between the chassis and the body, ask for the joint to be placed outside the flexing section and properly supported. A repair made in the middle of a flex point is a future failure — it costs nothing to do it properly at the time, and a great deal to do it twice.
Go back to whoever converted the vehicle; that wiring is theirs.
What this code means
The negative line of vehicle communication bus F is open circuit. Everything at U0082 applies — the join between chassis and body wiring, the flex point between them, the underbody exposure, and the free test of loading the vehicle or cycling the body.
U0006's instruction is the one to carry: inspect the partner conductor along the same length wherever a break is found, and replace a damaged section rather than splicing one wire.
On a working vehicle that instruction has extra force, because the damage is usually mechanical and localised — a strap, a load, a stone, a flex point — rather than the slow corrosion that takes one conductor at a time in a cabin. Whatever crushed or cut one wire almost certainly reached the other, and a vehicle that earns its living cannot afford to come back.
And where the loom crosses a flex point, the repair should restore the strain relief as well as the conductor. A splice at a flexing point is a future failure, and moving the joint out of the flex zone costs nothing at the time and everything later.
Likely causes
Start here
- Damaged data bus wiring · moderate
- Damaged wiring harness · moderate
- Poor wiring splice in an aftermarket installation · moderate
- Corroded or loose connector · easy
Less common
- Physical damage from road debris · moderate
- Failed bus terminating resistor · specialist
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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