U0051: Vehicle Communication Bus C (-) Open
What to do
Expect the entertainment, navigation and phone systems to have stopped. The car will usually drive normally.
One broken wire does this — see U0048 for why breaking either wire stops the whole network.
When the break is found, ask for the second wire to be inspected along the same stretch, and for a damaged section of loom to be replaced rather than one wire spliced.
There is a particular reason on this network. This wiring runs behind trim that comes off again and again — stereo installations, speaker upgrades, dashcam wiring, phone mounts, chasing rattles. A loom that has been disturbed several times over a car's life has had several chances to be damaged, so finding one break does not mean it is the only one.
Mention any work of that kind, including anything a previous owner had done.
What this code means
The negative line of vehicle communication bus C is open circuit. Everything at U0048 applies — including that the existence of this code establishes the network as a twisted pair rather than an optical ring.
U0006's instruction is the one to carry: inspect the partner conductor along the same length wherever a break is found, because the two run twisted together and whatever damaged one was in contact with the other.
And on an entertainment network there is a specific reason to take that seriously. This wiring runs behind trim that comes off repeatedly — for stereo installations, speaker upgrades, dashcam wiring, phone mounts, rattle chasing. A loom that has been disturbed several times over a vehicle's life has accumulated several opportunities for damage, and finding one break does not mean finding the only one.
Likely causes
Start here
- Damaged data bus wiring · moderate
- Corroded or loose connector · easy
- Poor wiring splice in an aftermarket installation · moderate
- Damaged wiring harness · moderate
Less common
- Failed bus terminating resistor · specialist
- Water ingress into connector · 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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