U009B — Vehicle Communication Bus I

U009B: Vehicle Communication Bus I — what it means, the affected system and what to check before replacing parts.

Meaning, symptoms, causes and checks

Vehicle Communication Bus I. Basic catalogue definition; diagnostic details have not yet been reviewed.

Affected system: Network communication

Symptoms

  • System warning may illuminate
  • Affected feature may be unavailable
  • Symptoms depend on the vehicle

Possible causes

  • Module power or ground loss, connector or network wiring fault, or a module that stopped communicating
  • Module power, ground, or connector fault
  • Vehicle-specific mechanical or control issue

What to check

  • Record all available module faults
  • Scan all accessible modules and record which modules report the communication fault. Check battery voltage, module power and ground, connectors, and network wiring using the vehicle topology.
  • Compare results with vehicle-specific service information
  • Verify the repair
  • Scan all accessible modules and record which modules report the communication fault. Check battery voltage, module power and ground, connectors, and network wiring using the vehicle topology.
  • Repair the verified cause and rescan all affected modules

Also written as: U009B-00, U009B00, UO09B (some scan tools add the fault-type byte, e.g. -00).