U0171: Lost Communication With Restraints System Sensor B

What it means

The reporting module has lost communication with Restraints System Sensor B. It sets this code when expected sensor messages are not received for a specified time.

How it works

Restraints System Sensor B sends crash or restraint-related information to the vehicle’s restraint system over a communication network. U0171 sets when the reporting module does not receive the expected messages from Sensor B for the required time.

Common causes

Most likely first.

1. Sensor B power or ground fault
2. Damaged or corroded sensor wiring or connectors
3. CAN bus fault
4. Restraints sensor B failure
5. Low battery voltage

Symptoms

• Airbag warning light
• Restraint system warning message
• Airbags or pretensioners may be unavailable

How to diagnose it

1. Scan the restraint system and other modules for related codes, and save event or freeze-frame data before clearing codes.
2. Check battery and charging voltage history for a low-voltage event that could have interrupted Sensor B communication.
3. Following the manufacturer's restraint-system safety procedure, inspect Sensor B’s connector and harness for corrosion, damage, or loose connections.
4. Verify Sensor B’s power and ground using the manufacturer's specification.
5. If power and ground are correct, test the communication circuit and network, then determine whether Sensor B itself has failed.

Common fixes

• Correct low battery voltage or a poor battery connection.
• Secure Sensor B’s connector or repair damaged wiring to it.
• Repair an open or poor power or ground connection to Sensor B.
• Repair the restraint network or replace Sensor B if circuit testing confirms the fault.

Can I keep driving?

The airbag warning means one or more restraint functions may be unavailable, potentially including airbags or pretensioners. Limit driving to what is necessary and arrange prompt diagnosis; restraint wiring requires the manufacturer's safety procedure.