Just looked at your photos in post # 62 and from tortrons shout out posts this computer control module does not incorporate OBD1 which musta come later in the Gen2 trucks... I dunno if my 86 truck has a ECM connector port under the drivers side dash -- I think not, it's been almost 4 months since I been in the truck... I believe tortron is also correct about Gen1s not having a CEL I've never seen one on my dash panel...

One of my favorite cars was a 1989 Chevy Celebrity 2.8L auto 4 door sedan... If I remember correctly it had no OBD1 but did have an amber colored dash CEL & a connector port under the driver side dash... If I remember correctly I learned to use a paper clip to bridge 1st & 2nd left side pins and the check engine light would flash like Morse Code to give trouble codes when the key was rurned on... Short & long pauses & quick light flashes... Had to be ready to count the # of flashes and wait for the pause before the next # flash... There was a list of codes either in the owners manual or online, I forgot... Had to replace the computer on that car at Chevy dealer, expensive $500+ but they said it would have the latest updates providing better MPG and big boost in power... They were not fibbing, burned rubber & could easily beat a Ford Mustang GT to 60MPH+


Anyway
Keep Safe People

Well anyway