U0059: Vehicle Communication Bus D (+) High
What to do
Disconnect the battery if the car is going to sit waiting for repair. That is unusual advice and there is a reason for it.
This fault has put battery voltage onto a network wire that every computer on that network is connected to — see U0005. And a network in that state cannot go to sleep, so the car stays awake and the damaging condition stays applied.
So the time the car spends sitting with the fault present is time those computers are being stressed. Disconnecting the battery stops both the drain and the exposure.
Be prepared for the repair to have two stages — the wiring fault found and fixed, and then whatever was damaged. A garage that reports further faults afterwards is not moving the goalposts.
The cause is nearly always something fitted after the car was built. A tracker, dashcam, alarm, stereo, light bar or tow bar, where a live feed was tapped next to the network wires or a self-stripping connector clipped onto the wrong one. Say what has been fitted, including by a previous owner — unplugging it and re-testing is quicker than any measurement.
What this code means
The positive line of vehicle communication bus D is being held high. See U0005 for the module-damage warning — battery voltage on a bus wire can destroy the transceiver in every module on that network.
And here it compounds with U0055's sleep argument in a way worth stating.
A bus held at battery voltage is both damaging and awake. So the vehicle is drawing current continuously while the condition persists — which means a battery that goes flat is not merely a symptom but a clock. The longer the vehicle sits with the fault present, the longer the modules are exposed.
Which produces a specific, unusual instruction: disconnect the battery while the vehicle waits for repair. That is normally advice about convenience. Here it limits the damage, and it is worth doing rather than leaving the vehicle to discharge itself over a week in a car park.
The cause is nearly always an added power feed — a live tapped beside the pair, a self-stripping connector on the wrong wire, a screw through a loom — and unplugging the device is quicker than any measurement.
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
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
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.
Sign in or create an account to add what you found about U0059.