B0099 code meaning
Roll Over Sensor
What B0099 means
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.
B0099 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyWorkshop only
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of B0099
- 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
Common causes of B0099
- Most likelyInternal fault of the rollover sensor built into the airbag control unit (module replacement)
- PossibleAirbag unit loose, mounted at an angle or after a crash no longer within its fitting tolerance
- Less likelyWiring or plug fault where a separate rollover sensor is fitted
- Less likelyRestraint controller software or configuration not matching the vehicle
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Rollover sensorSRS control module
What each part of B0099 means
| B | Body system: airbags, seat belts, power seats, lights and climate control. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 99 | The exact fault in that area. |
What to do next
- Note B0099 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about B0099
What does B0099 mean?
B0099 means "Roll Over Sensor". B0099 reports a fault in the rollover sensing that decides whether curtain airbags and pretensioners fire when a vehicle tips. It is a generic code, so it means the same on every make.
Is it safe to drive with B0099?
B0099 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will B0099 fail an emissions test?
B0099 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is B0099 to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will B0099 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.