First off, I generally get through electrical issues even if it takes a few weeks and foul words. I’ve got an issue with my Sonoma and it’s almost gotten me to the monkey with a typewriter point. So below is the Cliff’s Notes version…
What makes it tougher is that the factory manual (1995 through 2004) only has schematics for the 1997 and 2004 and mine is a 1998. Another one is the symptoms change constantly. I can’t possibly go through all of the changes and so on as it is way too lengthy so here goes; clipped sentences and all.
VEHICLE 1998 GMC Sonoma 2WD with a W Code 4.3.
Electrical anomalies last summer. Replaced BCM programmed to VIN and with all RPO codes. Key relearn took promptly. No issues at all.
Few weeks ago came out of Lowes. Start/die. Start die. Security light on and 30 miles to house. Jumped fuel pump relay on a grasp. Started/ran fine but Security light on. All else normal. Unplugged jumper but that was a fluke IMO.
Next day this happened. No start, security light on, temp gauge inop, gas gauge inop, low fuel light on, alternator light on. No Service Engine Light on/no DTCs, radio display flickers at times, driver’s door locks/not passenger side but pass side lock works fine . (Alternator charges fine even with alt. light on.) Now and then gas gauge will peg out far right. When driver’s door locks truck will not start. When door does not lock it will start and run. I will refer to this in future text as “glitches”.
Next day, started right up/ran fine but glitches still present. Drove it a hundred miles no issues other than glitches. Always restarted. Next day, no start/glitches still exist. This has been on and off for 2 weeks; mostly no start.
Last Friday started/ran fine. Saturday same old no start. Last Monday started 4 or 5 times that day no problem other than glitches. Started up Tuesday after sitting all night. Since then nothing.
When it starts it runs/drives fine; just the glitches ever present.
The Security light remains on and there are 3 protocols for a key relearn. None of the 3 will take and the Sec. light will not go off. GM Master Tech in a forum says “almost always” (almost…that word) it is due to no power at dash fuse 15, blown fuse, or no power at Pin 13 of the C4 connector at the PCM. All is fine in that area. It is not the battery, cables, or grounds. Various pin out checks have led nowhere.
There is a secondary issue that popped up 3 or 4 days later after this one but I will hold off on that one at this point to avoid clouding it even further. I even tried the 2200 ohm resistor bypass trick. No luck there either.
The thought of the BCM failing has crossed my mind but apparently my truck has an odd number that is a bit difficult to find. May have something to do with that very late production month of Oct. 98.
So if anyone has a guess I’m willing to listen and learn. My guess bag is getting near empty. I’ve had to wrestle a few in the past that led to a few weeks of on and off tracking but eventually I got there and found the reason. Right now I’m getting nowhere while dealing with a couple of other issues including one non-mechanical one which could be lethal.
My preference would be for a bullet proof way to rid myself of Passlock. Only thing Passlock is doing is keeping me from using the truck and which I am in great need of right now. Judging from the internet GM’s Pass Key and Pass Lock seem to be plagued with problems. Thanks in advance.