Air bag lights also affect seatbelts
While the system performs self-test procedures every time the ignition is switched-on, an airbag fault warning lamp should not illuminate whilst driving. Should it appear, the airbag(s) are unlikely to inflate as designed in the event of a collision. The result is greater risk of personal injury and is why a permanently-lit airbag warning lamp is an MoT Test failure.
Effect on seatbelts
Many people think that an airbag warning lamp relates solely to airbags. It does not. Airbags are part of a vehicle’s Supplementary Restraint System (SRS), which includes seatbelt pretensioners. These retract the belt, and clamp occupants to their seats in a crash. Its condition is monitored by the system’s ECU computer, which also controls the airbags.
Therefore, a fault in the SRS system means that not only will the airbags not operate but the seatbelt pretensioners are also unlikely to fire, as intended, leading to a likelihood of increased injuries in an impact. Consider also that an insurance company may question any injury claims, not only because the safety systems were not operating but also because the vehicle is, technically, unroadworthy – a state which is the driver’s responsibility to maintain.
Repair cost implications
Worried by the high costs of quality replacement airbags and control systems, many people are tempted to ignore an illuminated airbag light, because they perceive that it does not affect the day-to-day running of the vehicle. However, many airbag/SRS faults are caused by loose wiring connections. As long as the fault is diagnosed correctly, a repair may not even require replacement parts.
Finally, we do not advise that the enthusiastic DIYer attempts any repairs on the airbag/SRS system, because tampering with the system could activate the airbag(s), seatbelt pretensioners and, possibly, destroy the ECU.