What it means
Bus C 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
Bus C sends messages over a paired positive (+) and negative (-) conductor. U0054 sets when those two conductors are electrically shorted together, disrupting the signal and potentially cutting off communication to multiple connected modules.
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
- Scan all modules and preserve freeze-frame data, noting which modules are offline and whether other bus C line faults are stored.
- Use the wiring diagram to trace both bus C conductors through shared connectors, splices, and gateway connections.
- Inspect places where the paired wires are pinched, melted, rubbed together, wet, or poorly repaired, and check connector pins for bridging or corrosion.
- With power isolated as directed by the manufacturer, test for an unintended connection between bus C (+) and bus C (-).
- Check each conductor for shorts to ground or voltage and measure network termination against the manufacturer's specification.
- If no harness short is found, isolate gateway and module connections using the manufacturer's procedure to locate an internal connection between the lines.
Common fixes
- Separate and repair bus C wires shorted together, replacing damaged insulation as needed.
- Repair a connector with bridged, bent, contaminated, or corroded pins.
- Correct a failed splice or previous repair that joins the positive and negative conductors.
- Repair or replace a gateway or module only if testing confirms it internally shorts the bus lines.
Can I keep driving?
Avoid driving if communication loss affects braking, steering, engine, transmission, or other safety related functions, or if the vehicle enters limp mode. If only noncritical features are affected and the vehicle behaves normally, keep the trip short because several modules may lose communication.
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.