U0044
Vehicle Communication Bus B (-) High
What it means
U0044 means Vehicle Communication Bus B (-) High.
Check these first
- A short to voltage on the Bus B negative wire
- A failed transceiver holding the Bus B negative line high
- Harness damage shorting the Bus B negative wire to power
- A faulty module on the Bus B network
What to do next
- Read the code and check module communication status on a scan tool
- Measure Bus B negative voltage with the key on
- Test the Bus B negative wire for a short to voltage
- Unplug modules one at a time to see if the line returns to normal
- Replace the module that holds the Bus B negative line high
- Clear the code and retest
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Updated
Generic SAE J2012 definition. Last updated 2026-10-10.