U0063: Vehicle Communication Bus D (-) Shorted to Bus D (+)
What to do
Disconnect the battery if the car is standing, and do not buy a new battery until the wiring is fixed.
The two wires carrying this network are touching each other, which cancels the signal completely — so the network stops rather than working badly.
And a network that has stopped cannot pass on the message to go to sleep. So every computer that was awake stays awake, and the battery flattens reliably and fairly quickly.
Which means a car recovered dead, with this fault stored once it is charged, has one problem rather than two — and it also means buying a battery first simply provides more current for the fault to drain. That is how people end up buying two.
One test confirms this with no manufacturer data at all: near zero ohms across the pair, which is wrong on every network there is.
Two wires twisted together only touch for physical reasons: a loom crushed by a panel, a bracket or a fixing; a screw put through the harness during a repair or an accessory installation; water bridging a connector; rodents.
What this code means
The two lines of vehicle communication bus D are shorted together. See U0009 for why joining a differential pair cancels the signal completely, and U0036 for why this is the one fault on a lettered bus that needs no manufacturer data to confirm.
One consequence follows from U0055 and it is the practical one.
A bus that has stopped entirely cannot carry a sleep message either, so every module that was awake when the short appeared stays awake. The vehicle will flatten its battery, reliably, and quite quickly — faster than the slow drains at U0058, because nothing settles at all.
So a vehicle recovered dead, with this code stored once it is charged, has one fault rather than two — and the battery should be disconnected rather than left connected while the vehicle waits.
And there is a diagnostic order that follows from it. Charge or replace the battery only after the short is repaired. A battery flattened repeatedly by this fault may itself be damaged by the time the wiring is fixed — but replacing it first simply provides more current to discharge, and it is how an owner ends up buying two.
Likely causes
Start here
- Bus wires shorted together · moderate
- Damaged wiring harness · moderate
- Water ingress into connector · moderate
- Damaged data bus wiring · moderate
Less common
- Poor wiring splice in an aftermarket installation · moderate
- Corroded or loose connector · easy
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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