Body, generic

B0099 Roll Over Sensor

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

B0099 reports a fault in the rollover sensing that decides whether curtain airbags and pretensioners fire when a vehicle tips. Bosch integrates rollover sensors in its base airbag control unit, so the sensor is often part of the module. A Delphi patent shows the principle: roll rate and low-g vertical acceleration give roll angle and rate, which are compared with deploy and no-deploy curves, while a high-g lateral accelerometer acts as a separate arming check. FMVSS 226 requires a monitored readiness indicator where ejection mitigation deploys in a rollover; Karma recalled the 2018 Revero because its rollover sensing was not enabled. FCA uses the code: recall Y79 (2021 Grand Cherokee, 2022 Wagoneer) has technicians check for B0099-96 before reflashing the restraint controller, without defining it. The airbag lamp lights.

Likely causes

Internal fault of the rollover sensor built into the airbag control unit (module replacement)
Airbag unit loose, mounted at an angle or after a crash no longer within its fitting tolerance
Wiring or plug fault where a separate rollover sensor is fitted
Restraint controller software or configuration not matching the vehicle

Symptoms

  • Airbag warning lamp on
  • Curtain airbags and pretensioners may not fire in a rollover
  • Safety note: airbag control unit with rollover sensing; work only de-energised (battery off, wait time) at a specialist workshop

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–1,200
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

rollover sensorsrs control module

Related codes

B0090B0091B0095B0096

References: static.nhtsa.gov, bosch-mobility.com, patents.google.com, law.cornell.edu.