Toyota Repair: toyota 4runner question, toyota 4runner, diagnostic connector

Question
When i got my stereo installed at Magnolia i realized a couple of things that went wrong.... My horn stopped working, my airbag light is now permanently on, and my cruse control no longer works... i would take it back to Magnolia, but that was over a year ago... My husband is putting in a new clutch and he cant figure out where the problem is... any advice?   Thanks

Answer
They most likely wired it incorrectly.
Check the fusing for the horn.
Get the diagnostic code for the airbag. (If an older 4runner, short Tc & E1 in a diagnostic connector & count the ABS light flashes to get the code. If new, connect to a scanner. Then check the code.
Check the fusing for the cruise control.
They probably mis-wired the head unit. Taking power from an electrical system that can not handle the load.