What it means
Bus D lines shorted together. 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 over paired positive and negative lines. U0063 indicates that those two conductors are shorted together, so the control module detects a bus fault and connected modules may no longer exchange messages reliably.
Common causes
Most likely first.
- Bus lines shorted together
- Gateway module routing CAN messages incorrectly
- 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
- Record all module codes and freeze-frame details, checking whether communication loss is confined to bus D or also affects other networks.
- Identify which bus D modules are not responding and note any related line faults that can help localize the short.
- Inspect the paired bus D wires, connectors, and splices for crushed insulation, pin bridging, water, or repairs joining the conductors.
- With power isolated according to the manufacturer's procedure, test for unintended continuity between the positive and negative lines and isolate wiring sections to locate it.
- Check bus D termination and gateway routing against the manufacturer's procedure after the line-to-line short is ruled out.
Common fixes
- Separate and insulate bus D conductors that have rubbed or fused together.
- Repair or replace a connector with bridged or damaged terminals.
- Correct a termination fault if measurements are outside the manufacturer's specification.
- Repair or replace the gateway only if testing confirms it is contributing to the bus fault.
Can I keep driving?
Avoid driving if bus D dependent systems are affected, because multiple modules may lose communication or shut down. Stop if braking, steering, or another essential function is impaired; the fault can spread its effects across connected features.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.