Cause
Faulty airbag module or initiator
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.
Typically specialist work. Needs equipment or training most home workshops do not have.
Codes this can cause (31)
Codes where this is a likely explanation first, rather than merely a possible one.
- B0001 Driver Frontal Stage 1 Deployment Control Likely for this code High
- B0002 Driver Frontal Stage 2 Deployment Control Likely for this code High
- B0003 Driver Frontal Stage 3 Deployment Control Likely for this code High
- B0004 Driver Knee Bolster Deployment Control Likely for this code High
- B0005 Collapsible Steering Column Deployment Control Likely for this code High
- B0010 Passenger Frontal Stage 1 Deployment Control Likely for this code High
- B0011 Passenger Frontal Stage 2 Deployment Control Likely for this code High
- B0012 Passenger Frontal Stage 3 Deployment Control Likely for this code High
- B0013 Passenger Knee Bolster Deployment Control Likely for this code High
- B0020 Left Side Airbag Deployment Control Likely for this code High
- B0021 Left Curtain Deployment Control 1 Likely for this code High
- B0022 Left Curtain Deployment Control 2 Likely for this code High
- B0028 Right Side Airbag Deployment Control Likely for this code High
- B0029 Right Curtain Deployment Control 1 Likely for this code High
- B002A Right Curtain Deployment Control 2 Likely for this code High
- B0030 Second Row Left Side Airbag Deployment Control Likely for this code High
- B0031 Second Row Left Frontal Stage 1 Deployment Control Likely for this code High
- B0032 Second Row Left Frontal Stage 2 Deployment Control Likely for this code High
- B0033 Second Row Left Frontal Stage 3 Deployment Control Likely for this code High
- B0038 Second Row Right Side Airbag Deployment Control Likely for this code High
- B0039 Second Row Right Frontal Stage 1 Deployment Control Likely for this code High
- B003A Second Row Right Frontal Stage 2 Deployment Control Likely for this code High
- B003B Second Row Right Frontal Stage 3 Deployment Control Likely for this code High
- B0040 Third Row Left Side Airbag Deployment Control Likely for this code High
- B0041 Third Row Left Frontal Stage 1 Deployment Control Likely for this code High
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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