U0032: Vehicle Communication Bus A (+) High
What to do
This is one of the faults that can damage things rather than just stopping them. Full battery voltage has got onto a network wire, and every computer on that network is connected to it.
Be prepared for a repair in two stages — the wiring fault found and fixed, and then whatever was damaged while the voltage was present. A garage that reports further faults after repairing the wiring is not moving the goalposts.
One thing worth asking for here specifically. This network is identified only by a letter, so which computers were connected to the damaged wire is not obvious. Ask for the car's network map to be read before the repair rather than after — it is the record of what was exposed to the voltage, and it is far more useful established up front.
Two questions will very likely find the cause, and both are yours to answer. Has anything been fitted to the car — alarm, tracker, dashcam, light bar, tow bar, stereo? And has the battery ever been connected the wrong way round, or jump-started backwards? People remember that and rarely mention it.
What this code means
The positive line of vehicle communication bus A is being held high. See U0005 for the warning that matters most: battery voltage on a bus wire can damage the transceiver in every module on that network, so the repair may have two stages.
One thing is specific to a lettered bus and it makes this worse rather than better.
U0028 explains that these networks are not identified by their names. So the set of modules exposed to the voltage is not obvious either — and a workshop that has not read the vehicle's topology does not know which modules were on the affected pair. That matters when the wiring is repaired and something still does not work: the list of candidates should have been established before the repair, not after.
So the topology step is not administrative here. It is the record of what was exposed.
Otherwise the cause list is U0005's, and the two productive questions remain: what has been fitted to the vehicle, and has the battery ever been connected the wrong way round.
Likely causes
Start here
- Wiring shorted to voltage · moderate
- Poor wiring splice in an aftermarket installation · moderate
- Faulty aftermarket alarm or immobiliser installation · moderate
- Damaged data bus wiring · moderate
Less common
- Damaged wiring harness · moderate
- Corroded earth connection · moderate
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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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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