U0172
Lost Communication with Restraints Rear Sensor \"B\"
What it means
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?
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical.
Most likely causes
Rear sensor B unpowered
highOne of the most commonly reported causes for this code — check this first.
Wiring to rear sensor B broken
mediumA plausible cause — test and verify before replacing parts.
Gateway module routing CAN messages incorrectly
lowLess common, but worth ruling out after the more likely causes.
Related help
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