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<DIV><FONT face=Arial size=2>If you have an o-scope and can see a square wave
signal between ground and one of the diag-terminals then you can be pretty sure
that its ALDL. If you can trap the signal and see if it repeats then you
can figger out about how many bytes are there. if its a really small amount like
8 - 10 then there probably needs to be a request sent to the ECM for it to start
sending lengthy amounts of data, and the data being sent without this request is
very basic.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>With a DMM, if using like a "John Fluke" 73,77,83
series DMM ($100- $150 range) you can see the voltage bar LCD points pulsing up
and down rapidly as the RMS DC value changes (as a result of the varying duty
cycling of the DC signal based on the characters being represented) in some
repeating pattern.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>With an analog needle, you won't see much but a
steady DC voltage somewhere between 0 and 5, needle moving very very
slightly.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>I think caddilac had an onboard diagnostic viewing
system built into the RADIO controls system??? Jeffrey M's wife had a car
with that system in it. You might ask him if it was a 95 and to clarify my vague
memory.</FONT></DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>P.S. .. anyone out there have flow numbers on a
complete stock TPI intake system, and Accel / Ligenfelter units?
;-)</FONT></DIV>
<DIV> </DIV>
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style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A href="mailto:jhaines@lingenfelter.com" title=jhaines@lingenfelter.com>Jason
R. Haines</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A href="mailto:gmecm@diy-efi.org"
title=gmecm@diy-efi.org>GMECM</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, September 02, 2000 12:22
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> ALDL data</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>What is an easy way to check to see if an ALDL
port has any data coming from it at all (if it is wired correctly etc.)? I
have a custom car I want to read the data from but a Tech 1 and a Tech 2 won't
communicate (neither will Diacom). Anything I can check with a voltmeter? What
about using the Diacom cable (parallel port) and some kind of software to see
the raw data (if any exists)? I think I might also have a serial port ALDL
cable (for some other software) that I could use.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>BTW - the engine is a Cadillac Northstar engine
with a 1994 ECM (I think it is ECM part number 16197429) and a custom harness
(no Cadillac dash, no electronic throttle etc.).</FONT></DIV>
<DIV><FONT face=Arial size=2><BR>Jason</FONT></DIV>
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