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Home / Codes / U0073
DTC code page

U0073: Control Module Communication Bus Off

Quick answer: A module detected that the CAN communication bus dropped into a bus-off state and normal messaging stopped.

Drivers also search this fault as CAN bus off, control module bus off, CAN communication failure, bus off network code.

Severity: high Family: network Related paths: 14
Meaning

What U0073 usually means

U0073 means the vehicle communication network did not just have one late message; the bus itself fell into a bus-off condition where one or more modules effectively stop participating. In real diagnosis that usually points to a wiring short, water intrusion, a module pulling the network down, or a voltage problem that made normal CAN traffic collapse.

Fast triage

Start here before chasing parts

  • Scan first: save freeze-frame and pending codes before clearing anything.
  • Confirm the complaint: compare the stored code with current drivability symptoms.
  • Use context: trims, live data, and related codes usually narrow the fault faster than guesswork.
  • Work simplest to hardest: leaks, connectors, maintenance items, and known patterns before expensive components.
Initial checks

What to check first

  • Ask whether multiple warning lamps, no-communication scan-tool complaints, or intermittent starting issues happened at the same time because that pattern fits U0073 well.
  • Check battery voltage and charging stability early since weak system voltage can make a healthy network look broken.
  • Do not unplug modules randomly with the key on because that can add more network noise and confuse the picture.
Driving risk

Can you keep driving?

U0073 can leave the vehicle in reduced power, disable multiple systems, or create an intermittent no-start. If communication is actively collapsing, this is not a code to ignore or keep clearing.

High urgency: If symptoms are active, reduce driving and diagnose quickly before secondary damage builds.
Likely causes

Common causes behind this code

  • Short to ground or short to power on a CAN high or CAN low circuit
  • A failed module internally loading the network and forcing bus-off behavior
  • Low system voltage or unstable charging that makes module communication collapse
  • Water intrusion or corrosion in a splice pack, connector, or underhood fuse box
  • Recent wiring, aftermarket accessory, or module replacement disturbing the network

Cause phrases often tied to this code: CAN wiring short, module pulling bus down, water intrusion, low system voltage, corroded connector.

Diagnostic order

Suggested workflow

  1. Capture all module codes before clearing anything and note which modules still communicate.
  2. Verify battery and charging voltage so the network is not being blamed for a basic power-supply problem.
  3. Inspect CAN wiring, splice packs, and fuse-box areas for collision damage, water intrusion, or aftermarket taps.
  4. Measure network resistance and observe CAN high/low behavior if you have the proper wiring diagram and scope access.
  5. Isolate the offending branch or module only after confirming the bus truly is being pulled down.
Avoid guesswork

Common mistakes

  • Replacing the first module named by the scan tool before proving the network wiring and power feeds are stable.
  • Ignoring low-voltage history even though weak battery or alternator output can trigger broad communication chaos.
  • Clearing codes too early and losing the map of which modules were online and offline.
Repair path

Practical fix guidance

  • Repair the proven CAN wiring, splice, power-feed, or water-intrusion fault before condemning modules.
  • If one module is verified to pull the network down, confirm its powers and grounds before replacing it.
  • After repair, recheck full-module communication instead of celebrating because only the engine module came back online.
Vehicle context

Affected brands in this MVP

Brand hubs help broaden internal linking now and can evolve into make-specific diagnostic notes later.

Aliases and common searches

English phrases tied to U0073

Useful when the driver knows the wording but not the exact DTC yet.

  • CAN bus off
  • control module bus off
  • CAN communication failure
  • bus off network code
Related search intent

Queries this page can answer naturally

  • U0073 code meaning
  • what does U0073 mean
  • CAN bus off symptoms
  • control module communication bus off
FAQ

Quick questions about U0073

Does U0073 always mean the PCM is bad?

No. Wiring faults, low voltage, or another module loading the network are often more likely than a failed PCM.

Can a weak battery cause U0073?

Yes. Broad low-voltage events can destabilize module communication enough to set network codes.

Why do so many warning lights come on with U0073?

Because once the network collapses, several modules stop hearing each other and each system starts reporting its own loss-of-communication symptoms.