U0073 – Control Module Communication Bus “A” Off

Meaning:

When there's a problem with the CAN bus, the U0073 triggers
The U0073 is triggered when there’s a problem with the CAN bus

Problem with CAN bus making it hard for modules to exchange information and to communicate with scan tool.

Main Symptoms:

Possible Causes:

  • Open in the “A” CAN bus + or – circuit
  • Short to power or ground in “A” CAN bus circuit

Diagnostic Steps:

  • Pull all communication codes and address them first then this one last
  • Visually inspect all bus communication connections (connectors and wires) for breaks, shorts, opens, chafing, burns and melted spots
  • Reset all codes and do a test drive. If this code returns disconnect one control module at a time and see if the scanner can finally communicate with PCM

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