U0171: Lost Communication With Restraints System Sensor B
What does U0171 mean?
U0171 is a diagnostic trouble code indicating "Lost Communication With Restraints System Sensor B". The vehicle's main computer has lost its ability to communicate with a specific module over the data bus. This could be caused by a wiring fault, a blown fuse, or a failed control module.
Symptoms you may notice
- Check engine light (MIL) illuminated on dashboard
- Intermittent warning lights
- Erratic gauge readings
Estimated repair cost
Typical range in Australia (parts + labour)
Common causes
- Failed control module
- CAN bus wiring fault or short
- Blown fuse to the affected module
- Water intrusion in a connector or module
- Battery voltage too low
What should you do?
This code sits in the occupant restraint system. The airbags or pretensioners may not fire in a crash, and on some faults they can fire when they should not. The car will usually drive and feel completely normal, which is exactly why this one gets ignored. Have it diagnosed before you carry passengers, and do not clear the code to make the light go away.
Get a diagnosis for YOUR car
Code U0171 can mean different things depending on your vehicle. TorqueBot gives you a diagnosis specific to your make, model, and year.