What it means
A control module has detected that communication bus C is off. The code does not specify which module or the underlying cause.
At a glance
- Usually lights the warning light of the system that lost communication
How it works
Communication bus C carries messages among the modules connected to that network. U0075 indicates that a control module has detected Bus C offline, which can happen when poor connector contact or malformed messages disrupt communication, though the code does not name the source.
Common causes
Most likely first.
- Corrosion or poor contact in connectors
- One module sending malformed frames
- Gateway module routing CAN messages incorrectly
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 reachable modules and save freeze-frame and network codes to see which Bus C devices stopped responding and whether faults are shared.
- Inspect Bus C connectors and splices for corrosion, loose terminals, water intrusion, or damaged wiring.
- Use the wiring diagram to test Bus C conductors for continuity and shorts with power isolated as specified by the manufacturer.
- Check bus termination at the specified points and compare the measurement with the manufacturer's specification.
- If wiring and termination are sound, isolate Bus C modules to find one sending disruptive messages and verify gateway routing using the manufacturer's procedure.
Common fixes
- Clean, secure, or replace corroded or loose Bus C connector terminals.
- Repair damaged Bus C wiring or splices.
- Restore correct bus termination by repairing the faulty connection or component identified by testing.
- Repair or replace the module sending disruptive messages or correct a confirmed gateway routing fault.
Can I keep driving?
Limit driving if Bus C loss disables needed vehicle functions, and stop if any affected function is essential for safe control. The outage may leave some systems unavailable, though this code alone does not establish that the powertrain is in limp mode.
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.