U0059: Vehicle Communication Bus D (+) High

What it means

Bus D high-side line voltage above expected range. A communication loss with this module breaks any function relying on its data — diagnostic tools may show 'no response' and dependent modules can fall into limp mode.

At a glance

• Usually lights the warning light of the system that lost communication
• The engine or gearbox may go into limp mode

How it works

Vehicle communication bus D carries data between the modules connected to that network. U0059 means the control module has detected the positive (high-side) bus D line above its expected electrical range, potentially preventing reliable communication.

Common causes

Most likely first.

1. Wire shorted to battery
2. Gateway module routing CAN messages incorrectly
3. CAN terminating resistor (120 Ω) drifted out of spec

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Record all module codes and freeze-frame details first, looking for other bus D faults that appeared at the same time.
2. Check which bus D modules are unavailable and whether the high-line fault affects several nodes.
3. Inspect the bus D positive wire and connectors for contact with a battery feed, damaged insulation, or pin bridging.
4. With power isolated according to the manufacturer's procedure, test the positive conductor for an unintended connection to battery voltage and inspect affected sections.
5. Check bus D termination and gateway routing using the manufacturer's diagnostic procedure after ruling out a wiring short.

Common fixes

• Repair insulation damage where the bus D positive line touches a battery feed.
• Correct pin bridging or replace a damaged connector that is raising the positive line.
• Repair a bus D termination fault if it is outside the manufacturer's specification.
• Repair or replace the gateway only if testing confirms incorrect routing is responsible.

Can I keep driving?

Avoid unnecessary driving if warnings or features are affected, as bus D communication may fail and dependent modules may enter limp mode or shut down. Stop if an essential system is unreliable, since other functions can be lost as the fault worsens.