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John, Master A.S.E Automotive technician
Category: Chevy
Satisfied Customers: 9176
Experience:  A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician
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95 buick lesabre: Check engine light..intermitently..restarted

Customer Question

I hhave a 95 buick lesabre,3800. Check engine light would intermitently come on but would reset when restarted. the problem got worse. Then the transmission started only shifting at prescrided shift points. I tried to read the codes with a scan tool but it wouldn't read the computer. I have checked all fuses I could find. under hood and the right hand kick panel. I have tried three different Computers, one new prom chip and just tried a new transmission speed sensor just to rule it out. I have made some progress because the engine runs wonderful most of the time with only an occational check engine light. When the light is on it does stumbel and ocationally die at about 10 MPH. I have checked apll plugs and connections I can find. Any help would be wonderful!!
Submitted: 9 years ago.
Category: Chevy
Expert:  John replied 9 years ago.


A scan of the system is very important to help you narrow down the fault.The failure you describe sounds like a crankshaft error or a mass air flow sensor failure.The transmission is electronic controlled & the ECM determines when it shifts from input sensors.

Customer: replied 9 years ago.
I believe everything that you have said. If I may ask, What action would you take given the answer you have given Me? So Do you have any thoughts on why I can't read the computer? I figure it would be great if it would at leat read something!!
Expert:  John replied 9 years ago.
Try your scan tool on another vehicle to verify that it works.
Customer: replied 9 years ago.
I didn't have two vehicles to try the scan tool on. But I have tried two different scan tools. same problem, No communication. This problem seems to puzzle everyone that I have talked to about it. I was hoping you could shine some light on it from a diferent angle.


Expert:  John replied 9 years ago.

Take a look at the wiring to the ALDL.Check these circuits.

Right lower pin #16 should have 12 volts

Left lower #9 data line to ECM (tan wire)

upper left second pin #2 purple wire class 2 data to ECM

Upper middle pin #4 from left should be ground

upper next one #5 ECM ground

Upper far right pin # XXXXX(top right corner) keyless entry reciever module(blk/white)