OBD Codes List

Diagnostic reference · U0044

U0044

Vehicle Communication Bus B (-) High

System
Network communication (U code)
Lamp
Check Engine Light
Category
Network Communications

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

  1. Read the code and check module communication status on a scan tool
  2. Measure Bus B negative voltage with the key on
  3. Test the Bus B negative wire for a short to voltage
  4. Unplug modules one at a time to see if the line returns to normal
  5. Replace the module that holds the Bus B negative line high
  6. Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.