Question: My dad and I were working on his 3/4-ton 2003 Suburban last week, replacing a bad alternator. After he installed it, the "service airbag" light came on. It has been on since then, but there haven't been any other problems. Any idea of what could be causing the light to come on?
The alternator isn't directly related to the SRS (supplemental restraint system). So backtrack the installation of the alternator to be sure no wiring or connectors were damaged in the process. Then check all fuses. There's an underhood fuse block, as well as left and right under-dash fuse blocks. You might also try disconnecting the battery for about 15 minutes, and see if the light returns. If everything looks OK, you need the proper scan tool to retrieve the SRS diagnostic trouble code that triggered the malfunction indicator light. Attempting any kind of further diagnosis without getting the code(s) will be counterproductive. The problem may very well have been caused by the installation of the alternator, or it was a coincidence, or was even a fluke code induced by the charging system. An SRS trouble code may be as simple as a bad switch in a seatbelt buckle, or as complicated as an opening in an airbag inflator circuit.
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