Now I'm scared

[GPster]

Yesterday I got a good start on dismantling the S15. I had been removing the plastic dash parts and throwing them away. When I finished breaking out the windshield I covered the hood/dash with plastic to keep any water out of any sensitive electronics (Yes. I disconnected the battery). I found the computor and made sure it stayed dry but I was amazed at the size of the bundle of wires that was connected to it. I was told that there was only a few wires that actuallywere connected to the vehicles wiring harness and I thought that the computor could run alone as long as I left it's sensors intact.The radio wiring had been butchered for the installation of a CD player but it's removal cleaned that up. To gain access to the radio/speaker wiring the heater controls (no AC) had been broken but the wiring was still intact so I saw no problem un-plugging it and pulling out all the plastic/tin associated with it. Cleaned out the mess that was shrouding the computor. Next I continued with some other frivalous stuff, door switches and under dash lights. They were loose because they had been un-bolted before I broke the plastic dash out. They "tee"d into a harness so I was going to un-wrap it figuring that it was all one circuit and there would be a connector at it's start. I would take care of it totally rather than leaving a cut for a short. The white wire goes directly to the computor. I thought about that for a second. Probably a dash light that tells you the doors are open but suppose there's a safety that kills the engine if you put the truck in gear (automatic) with the door ajar. I'd better get back to trying to find a wiring diagram for this thing. I investigated a GMC drawing that I had that said all of the service publications were managed by Helm Inc. I went to there site an was informed that a wiring diagram for a '87 GMC S15 didn't exist in their files. Now what?  I went under the hood to be in somewhat familiar territory but I got as far as the gas vapor canistor. There's a wire on it too. I'm overwhelmed! New computor, digital camera and company all weekend I need someone to talk to me . GPster

[enjenjo]

As I told you Joe, there are only two wires on the ECM that have to be hooked up for it to run, however there are a bunch of wires that are there, that don't have to be hooked up, And it will still run.

The wiring diagram is acually a book, with several hundred diagrams. I have a buddy with an AllData link at his shop, he downloads what I need and prints it for me.

[WZ JUNK]

I bought a book online that is the factory GM service manual for the Caprice donor car I am using.  I think I gave $45 for the book used but they are $150 new.  I think it shows everything about the car.  I did some searches on the net to find the book.  It was a long time ago and I am not sure where it came from.  You might start at ebay.

John

[wayne petty]

ok   just what years and motor /transmission combo do you have.



on almost every computer controlled gm car and truck the computer harness goes through a bulkhead elbow so of fitting that is retained with a plastic clip on the inside. a big clip...not easy to see...

there is also a transparent connector with 5 to 12 wires in it.. that goes across to the dash area... this also disconnects...

these are the
switched ign power,
fused battery long term memory,
check engine light output,
a few wires for the aldl test connector ,data,ground,?
speed input from the dashboard sensor.  and probably transmission range selection..  park+N verses rev,OD,D,2,1   the ecm needs to know if it is in gear to .   and some models may have a wire from the brake switch..

and don't be worried.. the engine will run just fine with just the two proper power wires hooked up...

[GPster]

ok   just what years and motor /transmission combo do you have? and don't be worried.. the engine will run just fine with just the two proper power wires hooked up...

It's an '87
S15 2wd short bed pick-up with a 2.5L 4 cylinder and automatic transmission. I haven't crawled under it yet to try to identify which transmission (so that I won't appear to be a real dummy when I ask about the lack of park). The further I go the less I understand. I had directions to an S10 site but it's tied-up in a Windows 98 Favorites file and the old computor doesn't want to give it up. Then we'll have to figure a language that this new computor will listen too. When I said that the wires were cut to put in a different tape player it got more confusing when I found that they had cabbaged the original radio back in. The bed was gone (I took it off in the junkyard to make sure the frame was good). Yesterday the front sheetmetal and doors came off. Maybe tomorrow the firewall and floor will get cut loose so the cab can be rolled off. First look says that the engine/trans (and firewall/floor) will need to be sat back 7". This is (is this)fun! GPster