OBD-II code · Network
U0172 Lost Communication with Restraints Rear Sensor "B"
The Restraints Rear Sensor "B" has stopped transmitting on the vehicle data bus, so other control units no longer receive its messages. A second rear crash sensor is unreachable, affecting airbag deployment. Safety-critical. Typical causes are loss of power or ground at the module, an open or shorted CAN/LIN bus wire, a connector fault, or an internal module failure.
Is it safe to drive with U0172?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyRear sensor B unpowered
- PossibleWiring to rear sensor B broken
- 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
- 1–4 h
- Emissions test
- Usually unaffected
- Parts involved
- Restraints Rear Sensor, Can Bus Wiring
Related codes
- U0171Lost Communication with Restraints Rear Sensor "A"
- U016DLost Communication With Exhaust Gas Sensor Module B
- U0170Lost Communication with Restraints Front Sensor "B"
- U0173Communication Bus "C" Off
- U0174Lost Communication With Restraints System Sensor E
- U0175Lost Communication With Restraints System Sensor F
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.