2000 (build: Chevy Blazer LS 4.3 A/T A/C 4WD (no auto 4WD)

Okay, for starters, I got my self into this so don't feel too sorry lol I bought the truck knowing it had a trans issue, but I didn't want to see it junked. I have been lurking on here searching my butt off and have spent hours checking this thing out to the best of my ability using the resources available. I am (somewhat) hrowing in the towel and asking for help.My brand new Haynes is failing me. I am considering purchasing a GM manual but am on the broke side so I need some help. I'll keep the commentary down to a minumum from here on...


I am following the diagnostic flow charts the best I can with what I have... (no factory tools, no FSM) I have found many pinouts by searching but:

This is what I need to help myself:
Anyone have the pinout for the transmission electrical plug?

Anyone have wiring diagrams from an FSM?


My issue mimics the ignition switch related issues, but doesn't seem to be that simple.

- trans is in limp mode
- power to cluster fuse and ign C is intermitant
- DTC's: (the usual) P0740, P0753, P0758, P0785, P1860

more details for anyone willing to read and offer assistance:
- cleared codes, key on---> there is power to cluster. start---> lose power to cluster like usual start, but it stays gone, check eng light turns on quickly with P0740, P0785 and P1860. key off and back on and restart---> there is now power to cluster, SEL on, same DTC's still. Shift to drive---> there is still power to cluster, SEL on, same DTC's still, trans in limp mode(3rd gear). Shift to low---> lose pwr to the cluster again, SEL on, same DTC's, plus one more of the above, trans in limp mose (2nd gear). Drive down the road taking off in L then shifting to drive---> trans shifts hard to 3rd and sometimes the cluster comes back right away... sometimes it waits a while... wierdest part if; while the cluster is powered, the engine is running and the SEL is on, you clear the DTC's the cluster loses power again!!!! What the heck is going on?! anyone know?

- and BTW jumping power to the cluster or ign c fuses pisses the computer off and the truck won't idle :/

y'all follow that?

 

That is way too many transmission codes for them to be individual problems. I would bet your ignition switch is causing these issues.

 

I thought that too, but jumping power to the cluster fuse and/or the ign c fuse should make it go away, right? and not make the truck the truck not idle...

Everything seemed way too wierd for it to just be the ignition switch or do you disagree?

Can the pcm shut off power to that circuit? Or shut off power to the trans?

 

No, the only thing that can impact that circuit is the ignition switch. There may be other problems with that circuit (shorted wire somewhere) that is causing the the issues when you energize that circuit with an alternate source.

 

i saw this on a ford once. it wouldn't shift right and would die at odd times. he had a ground of the computer that was broke off the terminal.

 

FML! back to the drawing board!

happen to have the pinout for the trans plug? dashboard? ign switch? don't think I found any of those when i searched pinout / pin out / pinouts...


I know you must get frustrated with all of this, but I really appreaciate the help!

I am looking at "Anatomy of the Ignition Switch" right now... I might be on to something! I am losing power at ing C also and that is before the ign switch! so belay the trans plug pin out!

got anything telling me how power gets to ign c? what else does it power ? Ima go see if this Haynes manual is any help...


thanks again!!!!

 

i dont know how well of diagram haynes is going to get you. i can get you alldata diagrams monday if you let me know what you need. i know kyle has got it, (i get mine throught the school and can only access it there)

 

thanks man! I am plugging away at it atm... just found something odd and I'm trying a different jump to ign C, we'll see where this gets us

 

okay, I have NEVER been so happy and so embarassed at the same time in my life!!!!!


The something wierd i refered to in my last post was the ign c fuse not losing power... I musta goofed before (i hope lol) so the cluster died, only had like a volt there checking with the meter to the top of the fuse, pulled the fuse and checked it with the meter, mili volts on the vehicle side, 12 volts on the ign switch side! wtf?! check it with my test light and it was dim as heck! basically there was a lil tiny connection, but not a good enough one to actually do anything... funny, cuz a buddy of mine was scratching his head when his amp for his sub quit and I found the same issue with in 5 mins... just a super weak connection! took me five hours on mine!!!! agh!

thanks guys, guess i was just another idiot after all

 

mighta not been a timly fix, but it was a cheap one. glad you figured it out