i have an air bag light that flashes.
and have a p code p0092 passenger airbag failure.it s ok if you turn off passenger airbag.

does anyone know where to start in diagnosis?

Wish I could help ya.... Ya might try asking over at GM-Trucks.com

They have a section called Ask the GM Expert. He's a pretty helpful guy. And there's quite a few GM techs there, too.

Good luck finding your answer

Let us know how it goes.