OBD-II trouble code
B0099: Roll Over Sensor (Subfault)
The airbag/SRS control module detected a fault with the roll over sensor. Rollover-triggered protection such as curtain airbags and pretensioners may be affected, so this needs prompt professional attention.
Quick facts
- System
- Body
- Category
- Airbag / SRS Restraints
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $700
- DIY difficulty
- Shop recommended
What does B0099 mean?
B0099 is a body (B) code stored by the airbag control module. Its SAE-generic definition is 'Roll Over Sensor,' referring to the sensor the restraints system uses to detect a rollover or a large lateral/roll motion. On many SUVs, trucks, and taller vehicles the module uses this input to fire the side-curtain airbags and lock or fire the seat-belt pretensioners when a rollover is detected. The roll over sensor may be a standalone unit or integrated into the airbag control module / an inertial (roll-rate) sensor cluster, so confirm the exact part and location against your make's service data.
The module sets B0099 when the roll over sensor's signal, supply, or ground is out of specification — an internal sensor fault, a wiring open or short, a corroded or backed-out connector, or a supply/ground problem. A two-digit symptom byte appended to the code identifies the type of circuit defect (open, short to power, short to ground, or performance). Because rollover sensing depends on the sensor being mounted solidly and level, a loose mount, a disturbed connector after interior work, or a sensor that was knocked out of position can all trigger the code.
This is a supplemental restraint fault, not a driveability fault: the vehicle drives normally, but rollover-triggered protection may not perform as designed, and airbag circuits carry a small risk of unintended deployment when mishandled. SRS diagnosis and repair should be performed by a qualified technician who can safely disable the system, and the fault should not be left unrepaired.
Common causes
- Failed roll over / roll-rate sensor
- Corroded, backed-out, or loose connector at the sensor
- Damaged or chafed wiring in the sensor circuit
- Open, short, or high resistance in the sensor's signal, supply, or ground
- Loose or improperly mounted sensor after interior or console service
- Faulty airbag/SRS control module (when the sensor is integrated)
Symptoms
- Airbag / SRS warning light on
- Stored B0099 fault (often with a two-digit symptom byte) in the restraints module
- No effect on engine or driving performance
- Fault that may appear or clear with vehicle motion or after interior work near the sensor
Diagnostic steps
- 1.Use a scan tool that can access the airbag/SRS module and record B0099 with its full symptom byte and any companion codes.
- 2.Locate the roll over sensor for the specific make and model; determine whether it is standalone or integrated into the airbag module.
- 3.With the system safely disabled per service procedure, inspect the sensor connector for corrosion, backed-out terminals, or a loose fit.
- 4.Verify the sensor is mounted securely and in its correct orientation — rollover sensing depends on a solid, level mount.
- 5.Check the sensor's power and ground against specification, and inspect the harness for chafing or damage.
- 6.If wiring, connector, mount, power, and ground all check out, the sensor itself is the likely failure; on integrated systems this may mean the control module.
- 7.Repair the wiring/connector, re-secure or replace the sensor, then clear codes and confirm the SRS light stays off.
Repair cost
$100 – $700
Re-securing a loose sensor or repairing a connector can be inexpensive, while a failed roll over sensor typically runs a few hundred dollars including diagnosis. SRS diagnostic time is usually $100-$200. If the sensor is integrated into the airbag control module, the repair can be considerably higher. SRS work should be done by a qualified technician.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with airbag / srs crash sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.