U0073
System
Network (CAN Bus)
Scanner required
Full-system scanner (engine, ABS, SRS, transmission, service resets)

Control Module Communication Bus Off

Understand U0073, common causes, and the right TOPDON scanner to diagnose it.

The CAN bus is offline — no module communication. Often wiring, termination, or a module shorting the bus.

Common symptoms

  • Multiple warning lights
  • No-start
  • Gauges dead
  • Many U-codes at once

Typical causes

  • CAN wiring damage
  • Failed module pulling bus down
  • Corrosion in DLC or junction connectors
  • Aftermarket device on OBD port

What scanner do you need?

Full-system scanner (engine, ABS, SRS, transmission, service resets)

Use live data and freeze frame to confirm the fault before replacing parts. ABS, SRS, and network U-codes usually require a full-system scanner.

Diagnostic tips

  • Record freeze frame data when the code first sets
  • Clear the code only after fixing the root cause
  • Check for related pending codes that point to a common issue
  • Verify battery voltage is above 12.4V before chasing sensor codes

Recommended TOPDON scanners

Frequently asked questions

Can I diagnose U0073 with a basic code reader?
U0073 may set in the engine module, but related diagnostics often benefit from an enhanced or full-system scanner with live data and freeze frame.
Is it safe to drive with U0073?
It depends on the code and symptoms. Flashing check engine lights and misfire codes should be addressed immediately. Consult a professional if unsure.