What does it mean?
B1231 is a Body (airbags, seat belts, body electronics) fault code. It indicates: SAS Control Module Activation (Deployment) Control Freeze .
Symptoms
- The airbag warning lamp stays on continuously from key-on
- Airbags and seat belt pretensioners will not deploy in a collision
- Some scan tools cannot clear the code even after the wiring is repaired
- Seat belt reminder behaviour may be abnormal
- Additional restraint system codes are usually stored alongside this one
Likely causes
- The module has recorded a deployment or crash-level event and has locked itself out
- Internal failure of the deployment driver stage inside the restraint control module
- Low or unstable module supply voltage from a weak battery, poor charging, or a corroded ground
- Water damage to the module, which is often mounted low in the centre tunnel area
- A used or unprogrammed replacement module fitted from a vehicle whose airbags had deployed
- Corroded or damaged module connector affecting the deployment control circuits
How to fix it
- Treat this as a safety fault; the restraint system is out of action until it is properly repaired
- Record every stored restraint code and the event history before erasing anything
- Check battery condition, the module power feed, and the restraint ground point for corrosion or high resistance
- Inspect the module and its connector for water intrusion, accident damage, and bent pins
- Attempt an erase only after the wiring is confirmed good; a code that returns immediately indicates the module is locked or failed internally
- Replace the restraint control module with a correct new unit and program it to the vehicle, never fitting a used module from a deployed vehicle
- Verify the airbag lamp completes its normal bulb check and then goes out