Have a 96 Blazer LS 2 door.

I am totally ignorant of GM wiring and components as I have not had one in over 30 years.

None of my front dash and or rear side speakers work.

Door speakers do work.

Verified the Metra harness connector was wired correctly to the Pioneer head unit, even switched front/rear factory plug connectors so I know front/rear output is there. Even switched head units.

Yes I checked and made sure speakers were there also.

I need info on the harness routing and connector locations for the audio so I can track down the problem. Anyone that can help I would greatly appreciate it.

Also, there is a gray and a black "box" taped together with gray foam around them just to the left off the steering column down low and just behind the lower panel. Gray box has a board with black resistors on it, and black box has an electronics circuit board plugged in it (both inside what looks like dead end connectors. Anyone know if this is factory and what it's purpose is?

I found an alarm horn under the hood with wiring cut off, so I am concerned someone hacked up the harness, and since GM used regular black electrical tape, very hard to tell what's not original.

Thanks

After doing some checking under some other search terms, looks like the oem speakers are junk, and possibly dead??? Odd that both rears and both fronts have nothing. Would still like wiring info, and any info on the two odd boxes I found under the dash.