OBD-II code · Network
U0173 Communication Bus "C" Off
A control module has detected that bus C is non-functional and shut its bus C interface off. Bus C is typically a tertiary segment used for diagnostics or specialized subsystems; modules on the segment fall silent simultaneously.
Is it safe to drive with U0173?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyBus C shorted to supply or ground
- PossibleOne failing module pulling bus C down
- Less likelyGateway module routing CAN messages incorrectly
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–8 h
- Emissions test
- Usually unaffected
- Parts involved
- Can Bus Wiring, Control Module
Related codes
- U0170Lost Communication with Restraints Front Sensor "B"
- U0171Lost Communication with Restraints Rear Sensor "A"
- U0172Lost Communication with Restraints Rear Sensor "B"
- U0174Lost Communication With Restraints System Sensor E
- U0175Lost Communication With Restraints System Sensor F
- U0176Lost Communication With Restraints System Sensor G
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.