U0030
Vehicle Communication Bus A (+) Open
What it means
U0030 means Vehicle Communication Bus A (+) Open.
Check these first
- An open in the Bus A positive wire
- A broken or corroded Bus A positive connector pin
- A module that has lost its Bus A positive connection
- Harness damage that cut the Bus A positive conductor
What to do next
- Read the code and check module communication status on a scan tool
- Test the Bus A positive wire for continuity end to end
- Check the Bus A positive connector pins for corrosion or backing out
- Measure bus resistance across the Bus A terminals
- Repair the open in the Bus A positive circuit
- Clear the code and retest
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Updated
Generic SAE J2012 definition. Last updated 2026-10-10.