First thing you need to do is make sure it has all the power and grounds working. The suspension control unit is behind the lug side cover on the left side. It is a pain to get to pulling out the interior lower part. You can pin out everything to make sure it is getting signals. It should have 2 power wires going to it, one for ignition on, and one that should read battery voltage. and also one ground. One fuse for it is in the fuse block on the right side of the dash, fuse 12, and the other one is under the hood in the fuse block, fuse 29. I would check those first. then work my way back. there is one groud for it that splits off to 2 points one is under drivers seat and the other one is in the back on the L/S D pillar usually around the rear liftgate motor unit. If it is getting good power and ground it should communicate. if it is trying to start then looses comm., it could be a bad connection somewhere. look throught that first befor you spend all that money.