1226519 ECM 160 baud ALDL output

[Programmer]

Check a couple things:
1. Centre coil button should be over 3K ohms
2. Ground strap from coil missing ?
3. Condenser failure ?
4. Poor distributor base ground ?
5. Corrosion between module and distributor ?
Lyndon.
-----Original Message-----
From: Louis Baiani <neptilou at attcanada.net>
To: gmecm at diy-efi.org <gmecm at diy-efi.org>
Date: August 24, 2000 7:26 PM
Subject: 1226519 ECM 160 baud ALDL output


>I made an adapter to read the ALDL info from the 1226519 ECM (closed
>loop carburator control - CLCC) for an 84 Century.
>
>With the ignition off, the data output is perfectly fine.  Once the car
>is started, the data is fine for a short time, then it becomes garbled,
>as in out of sync...enough to change all the values for that update
>interval.  Some times the data stays fine for a few mins, some times
>after a few secs.  Most likely will screw up when accelerating.  Not
>alternator noise, because I took off the belt and/or connector.  I have
>tried to filter with different supplies/chokes/caps to try to rectify
>the problem.
>
>Just today I thought again on what it could be.  The distributor was
>never isolated, so I unplugged the 4 terminal HEI connector to the
>computer.  I have found that this cured the problem, and the data is
>perfectly fine.  Could it be a bad HEI module? (internal amplifier?)
>Had anyone heard of this?  Should I use a scope to look at the signal?
>
>I would also like to find ALDL info on an 84 Vette, 5.0L (L83 engine).
>Please help.
>
>
>Louis
>
>
>
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