Lost Communication With Restraints System Sensor B
What it means
U0171 means the airbag (SRS) system has lost communication with restraints sensor B, one of the crash/occupant sensors it relies on. The engine and brakes are unaffected, so the car drives normally, but the airbag warning light comes on and the restraint system may not deploy correctly in a collision. Because it's a safety system, it should be diagnosed and repaired promptly.
Can I keep driving? The car drives normally, but a restraints sensor is offline and airbags may not deploy as designed — treat the airbag light as a safety issue and fix it promptly.
Real-world scan data
Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.
Common symptoms
What you'll notice
- Airbag (SRS) warning light on
- Restraints system sensor B unreachable when scanned
- SRS system may disable itself as a fail-safe
- Related restraints U-codes stored alongside it
Common causes
Most likely first
- Open, shorted, or chafed wiring to the restraints sensor (often under a seat or in a door/pillar)Likely
- Corroded or loose connector at the sensorCommon
- Damaged wiring from seat movement, a spill, or a prior collisionCommon
- Failed restraints system sensorLess often
- Bus fault preventing the sensor from reportingLess often
How to diagnose & fix
Work through it in order
- Scan the SRS system and confirm sensor B is offline (use care — SRS work carries deployment risk).
- Inspect the wiring and connector to the sensor for damage, corrosion, or a disturbed harness.
- Check the sensor's power, ground, and bus connections against the wiring diagram.
- Repair wiring or reseat the connector if that's the fault.
- If wiring is good, replace the sensor, clear the code, and confirm the SRS light goes out. Consider a specialist for SRS repairs.
FAQ
Quick answers
Is it safe to drive with U0171?+
Can I just clear U0171?+
Related codes
Read & clear U0171 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.