Seeing more & more of this as the platform ages, Applies to 2007-2013 GM fullsize trucks & SUV's. This is a 2011 Silverado 1500 4.8L with 273,xxx miles.
DTC B0085-00 set in the Airbag module, Open or Short to voltage in the Left Front Impact Sensor. The sensor is located in the left front door.
I don't even bother diagnosing this code anymore, Go straight to the wires that pass through the door jamb bellows! You will find the Purple/White or the White wire.....Or both broken. The Impact Sensor circuits are actually a auxiliary jumper harness that is normally pulled a little tighter than the main door harness. This of course puts more strain on those 2 circuits.
Trucks with crank windows may not be affected by this as there isn't a separate harness to pull & work the impact sensor jumper harness.
I like to add a section of wires to make the harness a little longer.....Spiral the wires around the main door harness to relieve it. If you try to simply splice the circuits back together, Especially if you solder the connections....It will break again in short order!
The harnesses must be pulled through the body side, Requires removing the Dash end cap trim, Door sill trim, And Footwell trim to release the Bellows locks & feed the harness through the opening in the cab/body.
Remove the Door Panel & release the Bellows locks.
Slide the Bellow down the harness (Away from the door) & carefully cut the 2 rubber "wings" that hold the Bellows to the harness.....I do not reattach the harness back to the Bellows.....Further relieving the harness. To disassemble it without cutting the "wings", You must disconnect all the door components & pull the harness out of the door enough to untape the harness from the "wings" by sliding the bellows toward the door.
You want the solder joints as small as possible, Don't let the solder wick down the wires! The longer the rigid spot in the wire is.....The more apt the copper strands are to break on either side of the solder joint!