Newbie ALDL question

[steve ravet]

Bill, a lot of it depends on what ECM you are talking to.  I think a lot
of the P4 ECMs have to be commanded to send data.  You might try
different resistors across the ALDL A&B pins to force different modes,
although you don't want to drive in some of those modes.  Last time I
checked at www.lindertech.com they still had MPSI scanners for
reasonable prices.

--steve

Ervinc90 at aol.com wrote:
> 
> I have been reading the archives on aldl for about a month or so.  I went
> ahead and built the ALDL interface that was posted which contained: a max232
> chip 9 resistors, 4 diodes, 6 capacitors and a voltage regulator.  I have
> downloaded the gcar2.exe and the pcmcomm program.
> 
> My question is this: Why am I not receiving continuous data in the monitor
> mode with the gcar2 program on a 386 with dos 6.2?
> 
> I have gotten spurts of data while checking for the connection with the ecm
> and noticed that everytime I turn the ignition on and off a set of 00 appear
> on the computer.  ( this leads me to believe that the max 232 chip is seeing
> something??)  I have double checked the circuit several times and even rebuilt
> a second from scratch.  I have tried this on a 91 corvette (ecm: 1227727) and
> a 95 chev c1500 (don't recall the computer).  I also noticed another interface
> diagram which utilized a 74ls07 instead of the transistors and resistors.  Is
> this somthing worth trying?  I am a metallurgical engineer that knows a little
> about circuits, but not enough to figure the problem out.
> 
> Thanks,
> Bill Carson