U0171
Lost Communication with Restraints Rear Sensor \"A\"
The Restraints Rear Sensor "A" has stopped transmitting on the vehicle data bus, so other control units no longer receive its messages. A rear crash sensor is unreachable, affecting rear 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.
The Restraints Rear Sensor "A" has stopped transmitting on the vehicle data bus, so other control units no longer receive its messages. A rear crash sensor is unreachable, affecting rear 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.
Common causes
- high
Rear sensor unpowered
One of the most commonly reported causes for this code — check this first.
Typical part cost: $110-1320
- medium
Wiring to rear sensor broken
A plausible cause — test and verify before replacing parts.
Typical part cost: $110-1320
See all causes + fix costs
Create a free Wrenchify account to unlock the rest for U0171.
Unlock causesFree forever · No credit card
First things to check
- 1Confirm the code with a scan tool and check for additional related codes.
- 2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.
Get the full step-by-step diagnosis
Create a free Wrenchify account to unlock the rest for U0171.
Unlock diagnosisFree forever · No credit card
Related codes
See related trouble codes
Create a free Wrenchify account to unlock the rest for U0171.
Unlock related codesFree forever · No credit card
Frequently asked questions
What does U0171 mean?
U0171 means "Lost Communication with Restraints Rear Sensor \"A\"". It is a generic OBD-II code that points to a fault in the network / communication.
What are the most common causes of U0171?
rear sensor unpowered; wiring to rear sensor broken; gateway module routing can messages incorrectly — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.
Can I keep driving with this code?
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical. Use the Wrenchify app for a full diagnosis specific to your vehicle.
Get the full U0171 diagnosis for your vehicle
Year, make, model + step-by-step repair help — free plan included.