Module d'airbag ou initiateur défectueux

The airbag assembly itself, or the squib that fires it, is out of specification.

This is the least common cause of an airbag circuit code and usually the last one to reach, because the wiring and connectors around these devices fail far more often than the devices do. A squib is a sealed pyrotechnic initiator with no moving parts and no wear mechanism; the loom that reaches it moves every day.

When the device genuinely is at fault, age and environment are the usual reasons. Moisture reaching the initiator changes its resistance. So does corrosion at the device's own connector, which on side and curtain units sits in a pillar where water can track down. A resistance slightly out of range rather than an outright open is the signature — it reads as a device fault where a broken wire reads as an open circuit.

Two practical points before anything is ordered. An airbag that has already deployed and not been replaced reports as a fault — obvious on a car with a visible bag hanging out, much less obvious on a used vehicle bought after a repair that was never finished properly. And a replacement must be the correct part for the vehicle: airbags are matched to the restraint strategy, and a module fitted from a different model can report as faulty or, worse, deploy to the wrong plan.

These are explosive devices and are transported, stored and disposed of under regulation. Fitting one is not a home repair.