NetNews Usenet Archive 1993 #1/NN_1993_1.iso/spool/rec/autos/tech/17375

Internet Message Format | 1993-01-04 | 5.4 KB

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Subject: Diacom ECM Software Review
Date: 4 Jan 1993 12:06:47 -0600
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Micro-review: It's awesome.

Mainframe review: Since I was such a good boy last year, Santa brought me a
copy of Diacom for Christmas.  As fate would have it, my car started doing an
intermittent stalling number just three days later, so I got a chance to try it
out in actual combat.  If you came in late, Diacom is a software package that
connects your IBM PC to your car's computer and gives you a realtime display of
all of the sensors as well as various internal ECM parameters.  There are
versions for GM and Chrysler.  I got the GM version.  The package includes both
3.5" and 5 1/4" disks, a comprehesive manual, and adaptor cables.  One end
hooks up to your PC's parallel port, the other goes in the car's diagnostic
connector (ALDL connector).  The program will work on any PC or compatible with
512K RAM.  However, the manual states that it will not work with Sharp 4500
series machines, Tandy desktops, or the Tandy 1400 laptop.  I used a Toshiba
T2200SX and it worked fine.

Using Diacom is easy.  You can run it right off the floppy or transfer it to a
hard disk with the supplied install utility.  You plug in the cable, run
diacom, and type in your car's VIN.  The screen now shows all of the parameters
the ECM will display.  Then you plug into the ALDL connector, turn the ignition
key on, and give the "link" command.  When the system links up, the display
activates.  The update rate depends on the particular ECM.  In my 88 Celebrity
with the "high speed" P4 ECM, I got 10 updates/sec.  My wife's 84 Buick with
the older C3 ECM gives 1 update/sec.  On the Chevy, I get readouts of 42
different parameters, from basic things like RPM, battery voltage, and coolant
temperature, to sensor values including MAP, EGR, and O2, to data unobtainable
any other way, such as ECM integrator counts, block learn multiplier counts,
and block learn cell number.

So what good is all this?  Well, my Chevy started this thing of stalling at
idle.  The check engine light never came on and no codes were set.  So what's
wrong with the damn thing?  Could be anything, right?  The shop manual has half
a page of things to check.  I plugged in Diacom and found the problem in 30
seconds.  Literally.  In less than one minute I had it figured out.  Diacom
showed me that all of the obvious culprits, like TPS or EGR were fine.  What
wasn't fine was the oxygen sensor voltage.  It would periodically drop to 0.
Half a second later, the car would stall.  Happened every time.  It couldn't
have been more obvious if the O2 sensor had jumped out and hit me on the head.
Most of the time, the voltage was OK.  It was fine while driving around.  But
as soon as the throttle went to 0%, the O2 output would become erratic.  When
it went to zero and stayed there, the car stalled.  I replaced the sensor and
it's been fine ever since.

Needless to say, I'm sold.  Diacom costs $300.  I figure I've already saved
around half that just in this one repair, either compared to taking it in to a
shop (not to mention the mental anguish of having Mr. Badwrench monkeying with
my car) or in terms of the time it saved me.  Since the oxygen sensor isn't
even listed as one of the possibilities under "stalling" in the shop manual, I
figure it would have taken me from 4 to 10 hours of grubby, painstaking
detective work before finding the real problem.  Add in that the O2 sensor
isn't the easiest one to test.

Diacom will also accumulate data over time, from 20 seconds to 20 minutes
depending on the ECM.  It will then dump this in a file compatible with DBase
or Paradox.  I read my data into Paradox and made a nifty graph showing O2
voltage vs. time.  Diacom is like someone handing you an aircraft searchlight
after you've been trying to find your way in the dark by striking matches.
Take the age-old question, "are my fuel injectors plugged"?  Diacom shows you
the fuel injector pulse width in milliseconds.  If your injectors are gummed
up, this number will go up as the ECM holds them open longer to compensate.
Diacom also gives you a direct readout of any stored trouble codes and lets you
reset the ECM from the keyboard (on some ECM's).  You can command the ECM into
ALDL mode, field service mode, normal mode, or system-backup (limp home) mode.
I can't imagine how I ever got along without Diacom.  Break your piggy bank,
rob a bank, sell your kids, do whatever it takes, but go get a copy of this -
it's that good.

Downside: although the disk isn't copy protected, it uses a dongle.  Normally,
I am morally opposed to buying programs that use dongles, but at least this one
isn't totally obnoxious, since it's part of the cable you have to plug into the
parallel port anyway.  There's a customer support number (not toll-free
though).  I called them once, before I bought it actually, to verify that is
would support my speed-density converted "V6 from Hell" and found the people on
the other end to be friendly and technically knowledgeable.

Disclaimer: I have no connection with Rinda Technologies whatsoever, other than
as a (very) satisfied customer.  Happy troubleshooting!

            - Michel

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