I have 96 s10, that has a 94 fuel tank, 98 dash and core support, i have dropped a 2000 0411 pcm, motor, tranny and the engine wiring harness, part of the wire harness is from a 98 black box pcm, i spliced the black plug from 98 (blacbox) to 2000 411 purple plug, i pulled fuel pump wire from 2000 pcm harness and vss signal and moved to the harness that had the black plug. everything worked great, truck ran and I had OBDII communication, got repairs done to fix codes, rescanned no codes Terrific!! Except I have power locks and windows but the 98 dash harness i have does not have power lock/window setup, so I went to a Junkyard and pulled the body harness from a 2000 s10 blazer so that would make a full set of wiring , pcm ,motor,transmission, all from same year. but i did chop off the wiring to the back of the blazer. so after installing the rest of the wiring truck starts fine everything works, locks, windows, no OBDII communication. have all body grounds connected as far as i know, I have power and ground at OBDII connecter, all fuses and relays have been checked. I cant figure out why OBD worked with have the 98 wiring and now that its all 2000 it doesnt work. please any help would be greatful. I do have 2000 4.3 wiring diagrams (complete) but i cant find anything for the rear wiring for the blazer, perhaps one of the wires i cut needs to be grounded? if anyone can provide wiring diagram for 2000 s10 blazer 4.3 that would help also.

 

SAE J1850 VPW

https://learn.sparkfun.com/tutorials...ed-with-obd-ii

If the vehicle runs properly, then you will need to run the wiring to the OBD2 connector.

There might be something interesting to you in the second page of this thread regarding factory information and wiring for multiple years.

https://blazerforum.com/forum/2nd-ge...s-20020/page2/