OK some back ground. Owned my 2003 Suburban for over 12 years now. It developed a mysterious battery drain that I think was down to the rear wiper think that is sorted. Also noted my main beam dashboard warning light flashed sometimes with everything off and car locked (lights do not appear to flicker). I think that is down to a faulty multi-function column switch. The truck sat for over a year due to a minor accident and covid. Finally finished repairs so bought it a present of a new battery. The dashboard sometimes doesn't come to life and was getting service 4WD and airbag messages on the drivers information centre (DIC). I pulled the dash to check the wiring as well a load of other things - it seemed to get better. However a persistent service airbag message remained (B0018 - passenger deployment loop). Couldn't find a problem. Came to the conclusion I was suffering from poor earths etc. So replaced the main power cables (+ve and -ve - what a pain they were to do) and doubled up the earth strap from the engine to the bulkhead. Started it up and dashboard was clear. Started it again to move it from the garage - still OK. Thought I would check just once more before getting it booked in for the vehicle test and.....Airbag and 4WD fault lights on. DIC has scrolling message about service airbag and 4WD....yet 4wd selector switch is working though when I put it in gear the gear indicator is lit but not the bar underneath showing which gear is selected. The battery light is on despite the engine running , the voltmeter isn't working and the temperature gauge is dead as well. (Oh yes replaced the lead from the alternator to the main power connector). I walked away....Went back half an hour later and it started up with everything working and no fault messages. Can anyone come up with a suggestion (yes I do have a gallon of petrol and matches as well!). Cant think what I have missed