U0073 Code: Control Module Bus A Off — Causes & Fix
U0073 means communication bus "A" has gone "off" (bus-off) — a module has stopped transmitting because it detected too many bus errors.
- Applies to
- All OBD-II vehicles (any make or model)
- Est. repair cost
- $60 – $900
- Time to fix
- 1–4 hours
What it means
Causes include a wiring short across the CAN pair, a failed module flooding the bus, or connector faults. U0073 is a generic OBD-II network/communication ("U") code defined in the SAE J2012 standard, so it applies to virtually any modern OBD-II vehicle regardless of make. These faults usually point to the vehicle's data bus (often CAN) or a module that has dropped off the network. Fix the wiring/module fault, then clear the code with a scan tool.
Symptoms
- Multiple modules not communicating
- Many warning lights
- Features dead; possible no-start
How to fix it
- 1
Check for bus shorts
1. Inspect the CAN wiring for shorts (to power, ground, or each other).
- 2
Find the offending module
1. Disconnect modules one at a time to find the one causing bus-off. 2. Repair/replace, then clear the code.
Frequently asked questions
What does "bus off" mean?
A module counts communication errors; if there are too many, it shuts off its transmitter to protect the network. That is the bus-off (U0073) state.
Last updated July 19, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.