1988 Buick Lesabre Alternator/Battery/computer, what did I

Tiny
MEDMAN
  • MEMBER
  • 1988 BUICK LESABRE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 88,000 MILES
Was a great car. It hasn't been driven much in last 6-8 months. I starded driveing it again but the battery kept loosing it charge, had to jump it off daily.
Well to find out if it was the battery or the alternator
I jumped it off and then disconected the negative cable from battery to see if the car would keep running on the alternator output, after about 30-40 seconds it cut off.
Now it won't start at all. It won't jump off. It won't start with a fully charged battery.

What happened when I disconected the neg. Cable?
Did I fry the computer or what? Where is the computer?
Please help
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Monday, January 5th, 2009 AT 8:34 PM

9 Replies

Tiny
BUDDYCRAIGG
  • EXPERT
I hate to be the barer of bad news, but cars with computers dont like that test.

First lets see if you killed the computer.

Find the ALDL connector under the dash, 99% of the time it's on the drivers side.

Locate the A and B pins in the connector.
They are in the corner of the connector side by side, not diagonal from each other.

Jumper the A and B pins in the ALDL connector with a paper clip and watch for the service engine light to flash 12.

And we'll go from there.
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Monday, January 5th, 2009 AT 9:13 PM
Tiny
MEDMAN
  • MEMBER
Hello again, I just finished jumping A and B pins turned key to on position, service eng. Light does not light up at all.
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Wednesday, January 7th, 2009 AT 3:23 PM
Tiny
BUDDYCRAIGG
  • EXPERT
Without the jumper in place.
Will the service engine light come on solid if you turn the key to on?
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Wednesday, January 7th, 2009 AT 7:47 PM
Tiny
MEDMAN
  • MEMBER
No it will not come on at all.
When my trouble first begun the battery lite and the service engine lite both would flash with engine running. I think that my only trouble was a bad alternator (until I disconected neg. Cable while running).
Please advise next step.
Thanks
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Thursday, January 8th, 2009 AT 3:16 PM
Tiny
BUDDYCRAIGG
  • EXPERT
These are not optimistic signs

check the ECM fuse. And hope against hope that it is blown.
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Thursday, January 8th, 2009 AT 4:37 PM
Tiny
MEDMAN
  • MEMBER
This afternoon when I checked if the check eng. Lite would come on I allso pulled the fuse compartment cover and checked every fuse in it. They were all good. I did not look to see which was the ECM fuse (just checked all fuses in fuse pannle under dash) so unless ECM fuse is located somewhere else it is good.
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Thursday, January 8th, 2009 AT 7:14 PM
Tiny
BUDDYCRAIGG
  • EXPERT
I'm not going to say that a dead ECM is your [i:7565da7519]only[/i:7565da7519] problem, but you're going to have to start there.
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Thursday, January 8th, 2009 AT 9:52 PM
Tiny
MEDMAN
  • MEMBER
Where is the ECM and how hard is it to get to?
If I decide to replace the ECM myself is there any precausions I should know beforehand to keep from frying the replacement?
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Thursday, January 8th, 2009 AT 10:34 PM
Tiny
BUDDYCRAIGG
  • EXPERT
It's under the passenger kick panel.
On some models, it may be behind the glove compartment.

Make sure the ignition is off.
Disconnect the battery
and then replace it.
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Friday, January 9th, 2009 AT 6:32 PM

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