Airbag light is on in my cts cadillac 2005 , and even with a passenger is sitting the passenger airbag is always off , best solutions without paying money ?

This may not necessarily be a passenger situation, much more common to be the drivers side....

This error will have a code associated with it, you need that to know the next step. A common problem is with the connections under the drivers seat. this seat moves automatically, and the connections seem to generate a low resistance, and then trip a code failure....

Whatever the code tells you, disconnect and reconnect all connections, on that circuit.

Remember that the air bag testing happens on power on, so to retest, you have to power off and restart..

Doc