First of all, how easy would it be to remove all 8 of the plugs. I know on some cars there’s always a few that are near impossible to get to with just a home spark plug socket.
Second, if the BCM is going out, how intermittent would the electrical problems be? I can go over a month with no problems then something wackyass will happen. Wipers won’t turn off or radio resets or interior lights come on. I don’t want to spend $500 on a new BCM and getting it flashed and a whole day taking the center console out if that is not the problem.
I have a 1996 GMC Suburban with the Vortec engine. I had to tear it apart and put it back together again last year. The plugs were about the easiest part.
IIRC, getting them out wasn’t hard at all. I just needed some different sized socket extensions, depending on what was in the way. It was all accessible from the top of the engine with a little reaching to get the ones nearest the firewall.
Putting them back in was another story. They were kinda deep and hard to get to with the valve covers and exhaust manifolds in the way. I ended up using some old air compressor hose wedged to the top of the plugs to get them started then finished them with the socket wrench.
As for the BCM, I have no idea. Haven’t had to deal with that… yet.
Problems with the BCM usually do start out intermittent. There’s a bunch of electromechanical relays on the board that will wear out with use, and plus the connections on the board can get corroded. The early GM BCM’s were definitely problematic, so I’d be pretty confident saying that’s the problem if you’re getting intermittent problems with a bunch of otherwise unrelated parts.
I think if you buy a brand new BCM, you don’t have to get it programmed; it just automatically associates itself with the first key chip and radio it gets plugged into. If you buy a used one, though, you need to get it flashed. The particular GM computer tool you need has been around long enough that your local independent shops or even a locksmith might have it, so it might be worth calling around. Another “worth a try” option is if you’re at all handy with a soldering iron, you can take the BCM box apart and see if there’s any corroded connections or obviously damaged relays you can clean up or replace.