ALDL data

[Dave Zug]

Drilling bosses and having a 'frankenstein' look on my hands isn't worth the savings OR performance gains to me (besides not having the capability to DIY).  That superram is pretty cool lookin'... sometimes buying into some of the popular aftermarket stuff is my reward for skimping on other things for so long... besides, we gotta support the aftermarket SOMETIMES... some of them guys are just like US, but all grown up and with jobs   ;-]


  ----- Original Message ----- 
  From: Mike Rolica 
  To: gmecm at diy-efi.org 
  Sent: Saturday, September 02, 2000 8:47 PM
  Subject: RE: ALDL data


  your better off in the bank and performance to build your own :)
    -----Original Message-----
    From: owner-gmecm at diy-efi.org [mailto:owner-gmecm at diy-efi.org]On Behalf Of Dave Zug
    Sent: Sunday, September 03, 2000 2:14 AM
    To: gmecm at diy-efi.org
    Subject: Re: ALDL data


    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?  ;-)

      ----- Original Message ----- 
      From: Jason R. Haines 
      To: GMECM 
      Sent: Saturday, September 02, 2000 12:22 PM
      Subject: ALDL data


      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.
       
      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.).

      Jason

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