Airbags

B0099 — Roll Over Sensor Circuit Fault (Subfault)

Severity: medium Drive with care, to a shop

What B0099 means

The supplemental restraint system (SRS) control module constantly monitors the roll over sensor, which measures vehicle tilt and roll. B0099 is set when the sensor signal or its circuit is out of range or missing. The module may then disable roll-related protection such as curtain airbags and seat belt pretensioners.

Symptoms

  • Airbag (SRS) warning light is on or flashing
  • Restraint system fault message in the cluster
  • Rollover protection may be disabled
  • Warning light stays on after the engine starts

Possible causes

  1. Failed roll over sensor or its internal electronics
  2. Damaged sensor wiring: open, chafed or shorted
  3. Corroded or loose connector terminals
  4. Sensor mounting disturbed or misaligned after a collision or repair
  5. Faulty SRS control module (less common)

How to diagnose

  1. Scan all modules with a tool that reads SRS codes and save the freeze frame data
  2. Look for other SRS codes that point to a shared cause
  3. Inspect the sensor connector and harness for water, corrosion or damage
  4. Check that the sensor is mounted securely and the area is not deformed
  5. Test circuit resistance and supply voltage following the factory wiring diagram
  6. Disconnect the battery and wait the time given in the service manual before unplugging any SRS connector
  7. Clear the code and see if it returns; if it does, replace the sensor
  8. If the sensor and wiring are good, diagnose the SRS module

Common fixes

  • Repair or replace the damaged wiring or connector
  • Clean the terminals and secure the connector
  • Replace the roll over sensor and calibrate it if required
  • Replace or reprogram the SRS control module if it is at fault

Questions and answers

What does B0099 mean?

It is a subfault code for the roll over sensor circuit in the airbag system. The SRS module is getting a bad signal or none at all.

Can I drive with B0099?

Yes, but airbags and rollover protection may not work in an accident. Have it repaired as soon as you can.

Can I just clear the code?

Clearing it only turns the light off for a while. If the fault is still there, the code will return and the safety system stays compromised.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.