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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.
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.
With an analog needle, you won't see much but a
steady DC voltage somewhere between 0 and 5, needle moving very very
slightly.
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.
P.S. .. anyone out there have flow numbers on a
complete stock TPI intake system, and Accel / Ligenfelter units?
;-)
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