U0073
Control Module Communication Bus 'A' Off
Your car has a communication problem between control modules. One module may be faulty, or the wiring and connectors on the CAN network may be damaged or loose.
- SEV
- 4/5
- DRIVE
- CAUTION
- DIY
- $20–$150
- SHOP
- $150–$1,200
Quick answer
AI-CITATION READYWhat it means
Can you drive with it?
Most common causes
- Faulty control module on the CAN network
- Corroded, loose, or damaged wiring and connectors
- Low battery voltage or charging system problems
Typical repair cost
DIY usually runs $20–$150. Typical shop repair lands around $150–$1,200, depending on the root cause.
01 / Definition
U0073 means the vehicle network has detected a problem on Communication Bus 'A', which is part of the CAN data network used by control modules to share information. The fault can be caused by a failed module, damaged wiring, corrosion, low system voltage, or a network short/open that prevents normal communication.
02 / Drive status
With caution. You may be able to drive short distances, but the car can lose important functions like engine, transmission, ABS, or stability control communication. If warning lights are on or the vehicle runs poorly, have it checked soon and avoid long trips.
03 / Symptoms
- Check engine light or multiple warning lights
- Intermittent no-start or hard start
- Loss of communication with one or more modules during scan
- Erratic gauges, warning lights, or dashboard messages
- ABS, traction control, or stability control faults
- Transmission shifting problems or limp mode
- Power steering, HVAC, or other electronic system issues
- Stored multiple communication-related trouble codes
04 / Causes
| 1 | Faulty control module on the CAN network | high |
|---|---|---|
| 2 | Corroded, loose, or damaged wiring and connectors | high |
| 3 | Low battery voltage or charging system problems | medium |
| 4 | Short to power, short to ground, or open circuit in CAN wiring | medium |
| 5 | Water intrusion in a module, connector, or junction point | medium |
| 6 | Aftermarket device, alarm, remote start, or stereo interfering with network wiring | low |
| 7 | Blown fuse or poor power/ground supply to a control module | low |
05 / Diagnostic sequence
- 01Scan all modules, not just the engine computer, and record every code and module that does not communicate.
- 02Check battery voltage, charging voltage, and all related fuses and module power/ground supplies.
- 03Inspect CAN wiring and connectors for corrosion, water intrusion, loose pins, damaged insulation, or rodent damage.
- 04Unplug aftermarket accessories that may share power or data wiring and see whether communication returns.
- 05Use a wiring diagram to locate Communication Bus 'A' and test for opens, shorts to ground, and shorts to power.
- 06If one module is suspected, disconnect modules one at a time to see when the network recovers.
- 07Repair wiring or replace the failed module, then clear codes and verify the network communicates normally.
06 / Repairs
| 1 | Charge or replace weak battery and repair charging system problems | $20–$300 |
|---|---|---|
| 2 | Clean, repair, or replace damaged connectors, terminals, and wiring | $20–$250 |
| 3 | Repair shorted, open, or corroded CAN bus circuits | $100–$600 |
| 4 | Remove or rewire faulty aftermarket accessories causing network interference | $50–$300 |
| 5 | Replace and program the failed control module if it is confirmed faulty | $300–$1,200 |
MFG / Manufacturer notes
These supplements add make-specific diagnostic framing. Pages without full matrix backing or lane approval stay guarded and canonicalize back here until they are explicitly approved for indexing.
- Open
Audi U0073
Expansion-candidate noindex child page
07 / Related codes
08 / FAQ
What does U0073 mean?
It means the vehicle has detected a fault in the CAN communication network on Bus 'A' or in a module connected to it.
Can a weak battery cause U0073?
Yes. Low voltage can disrupt module communication and set network fault codes.
Is U0073 always a bad control module?
No. Wiring, connectors, power supply, ground issues, and aftermarket electronics are often more common than a failed module.
Will clearing the code fix it?
Usually not. If the underlying network problem remains, the code will come back.
09 / Source and method
- DATA BASIS
- OBD-II REFERENCE + OBD2.HELP
- METHOD
- STATIC VALIDATION
- SAFETY
- INFORMATIONAL
This page combines OBD-II diagnostic reference data with OBD2.help generated diagnostic guidance for code meaning, likely causes, and repair direction.
Publishing uses deterministic schema and build validation, plus manual spot checks on representative pages before release.
Safety-critical diagnosis and repairs should be confirmed with a qualified mechanic, especially when the vehicle is misfiring, overheating, or losing power.