Wiring issue?
 

I've had a few issues recently rear their heads with my 2004 Avalanche. The first thing that happened was my instrument cluster became unreliable with the volt meter and the temperature gauges going off the scale and remaining there, the fuel and oil pressure haven't gotten out of control yet. Next my right taillight isn't working, changed the bulbs, nothing. I also got a check airbag light. Does anyone know if these items share a common wiring harness? or are the disparate discrepancies?