OBD Codes List

Diagnostic reference · U0026

U0026

Low Speed CAN Communication Bus (-) High

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

What it means

U0026 means Low Speed CAN Communication Bus (-) High.

Check these first

  • A short to voltage on the low speed CAN negative wire
  • A failed transceiver holding the low speed CAN negative line high
  • Harness damage shorting the low speed CAN negative wire to power
  • A faulty module on the low speed CAN network

What to do next

  1. Read the code and check module communication status on a scan tool
  2. Measure low speed CAN negative voltage with the key on
  3. Test the low speed CAN 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 low speed CAN negative line high
  6. Clear the code and retest

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Updated

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