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View Full Version : Bad LM??....most likely.


black86glhs
04-26-2009, 03:58 PM
I'm 99% sure the LM in my car thinks it belongs to Simon, it's broken. Here is what it is doing: #1...will not show codes using the key. #2...car idles great and has good throttle response, but once you hit 7-8 psi, it falls on its face and check engine light rears its ugly head. #3...Out of nowhere while cruising along, it will stutter violently and then the check engine light will go out and it is back to running good. #4...it gives codes 11,12,33. I was expecting to find an overboost code.
What do you guys think?

Edit: I got this last year from FWDP. Should be this one, ECU 1986/1987 Stage 3 GLHS Calibration.
turbovanmanČ
04-26-2009, 05:12 PM
Ha, I cursed you, do you have pins in your back????????? :eyebrows:

I would start with checking grounds. Do you have a spare stock LM to try?
black86glhs
04-26-2009, 07:33 PM
Ha, I cursed you, do you have pins in your back????????? :eyebrows:

I would start with checking grounds. Do you have a spare stock LM to try?Yeah, the curse gets everyone.:(
I went through the grounds when putting it all back together, but checking again can't hurt. I have a spare LM. It has it's issues, but I can at least see if it does stuff the current one doesn't.:nod: Figures, the damn thing started up good and idles nice. Can't be pain free if it is a TM.:rolleyes:
boboli
04-26-2009, 11:05 PM
I purchased an 86 glhs stage 2 lm from the dealer 6 years ago. I could never get the car to run right. A few months ago I decided to try and fix it. I got the car to run but every few days I would go out and turn the key and there would be nothing from the asd. I found if i unplugged the lm it would start working again. It would sometimes not show any codes as well.I refused to believe that it was the lm's fault since it had less than 10 miles on it since I got it and they're supposed to be rebuilt. I decided to buy an 87 stage 2 lm to see if the problem would go away. and it did:clap:. I think there may be an intermittent problem on the logic's circuit board that previous owners had sent in as cores and the rebuilders can't or don't fix. I am throwing my old one away so that it will plague no one else.
turbovanmanČ
04-27-2009, 12:05 AM
Yep, I've had numerous rebuilt ECM's I've bought for customers bad right out of the box, due to a crappy repair, :(
black86glhs
04-27-2009, 08:32 PM
Well, neither LM will let me read codes with the key. Only thing I had out was the inside harness, disconnected at the bulk head connector. The engine wiring stayed in the car. Obviously, I need to pull the bulk head connectorand verify nothing is fubar, but I can't think of anything else.:confused:
black86glhs
05-03-2009, 08:42 PM
Apparently, I did not tweak the terminals in the blue 25 pin LM connector when I got it running last year. Plus, one of them backed out while I was working on it. Now I just need to finish my air intake and button up some more interior pieces.:thumb:
Glad it wasn't the LM going/gone bad.:D