Cayenne S 955 Airbag Light On

[cgrupp81]

2006 Porsche Cayenne S with 129k miles on it. Bought it used a couple years ago and so far happy with it. It has been in at least one front passenger side collision, undocumented by previous owner or dealer. I only know from a body shop analysis.
(Carfax says nothing of course.)

Issue: Airbag light has been on for a long time (1Yr) and trips to 2 different Indy shops have given me 2 different fault codes. #1590 Airbag Disconnecting Relay upper limit value exceeded (attempted to clear but returns after vehicle started). Second shop said #1317 Instrument Cluster Open Circuit. I have read all the forums on Airbags Faults and heard about some related TSB's but cant find it online anywhere. I am not ready to take it to the dealer just yet (as both suggested), and would like to see if there is some advice here.

Questions: Do I start with the under seat examination of the connections first or is that barking up the wrong tree? Is it possible that the sensors were damaged and/or not replaced? What are your thoughts? Thx.