U0171

Lost Communication With Restraints System Sensor B

Communication network (airbag/SRS) Generic OBD-II Medium

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.

Medium

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.

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?+

The car drives fine, but with the airbag light on the restraint system may not protect you correctly in a crash. It's a safety fault — get it repaired quickly.

Can I just clear U0171?+

Clearing it turns the airbag light off temporarily, but the fault returns and the system stays compromised. The wiring or sensor must be repaired.

Related codes

Often seen with U0171

U0151Lost Communication With Restraints Control U0170Lost Communication With Restraints System U0172Lost Communication With Restraints System U0168Lost Communication With Vehicle Security C

Read & clear U0171 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

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✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX