U0015 Moderate Generic / SAE

U0015: Medium Speed CAN Communication Bus (-) Open

Network and Communication Bus Signal and Bus Off

What to do

The car will almost certainly drive normally. A group of electrical fittings will have stopped working together.

Do U0012's free check first: open and close each door and the tailgate slowly, and watch whether anything changes. If it does, the break is in the rubber concertina between that door and the body, and it is a small repair.

One thing worth knowing about where this fault usually is. This network reaches every door, the tailgate, the seats, the roof and the boot — and each of those is a separate assembly with a plug where the wiring crosses into it. Those plugs are where breaks happen, because that is where the wiring gets disturbed by trim removal, seat movement, hinges and water.

So mention anything that has had trim off: seats out, carpets lifted, a boot liner fitted, speakers or a stereo installed, sill trims removed.

And ask for the second wire to be checked wherever a break is found. The two run twisted together, so whatever damaged one was touching the other.

Check your lights and indicators before driving at night.

What this code means

The negative line of the medium speed data bus is open circuit. See U0003 for what an open does to a differential pair, U0006 for why the partner conductor must be inspected too, and U0012 for the door harness boot that causes most of these.

One point belongs here because this bus reaches more separate assemblies than any other on the vehicle: the break is more likely to be at a connector than in the middle of a wire.

A high speed bus links a handful of modules along a short backbone. This one reaches every door, the tailgate, the seats, the roof and the boot — and each of those is a separate assembly with its own connector where the loom crosses from the body into it.

Those crossings are where the breaks are, because they are where the harness is disturbed by trim removal, by seat travel, by door hinges and by water.

So the search is a list of joints rather than a length of wire, and that is quicker: unplug, inspect, reseat, re-test at each crossing, rather than tracing a conductor end to end.

Likely causes

Start here

Corroded or loose connector · easy
Broken wire in the door harness boot · moderate
Damaged data bus wiring · moderate
Damaged wiring harness · moderate

Less common

Water ingress into connector · moderate
Failed bus terminating resistor · specialist

Symptoms

Components involved

Information, not instruction

CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.

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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