Hacking the DataStream

[gregs78cam]

So you want to be able to datalog, or view some seemingly insignificant piece of data coming from the ECM, or you need to see something that GM should have put in the datastream, and left out. Here ya go. I learned how to do this by looking through 93V8S10's AWESOME P4 PCM files and making small tweaks.

First you have to figure out if the ECM actually stores that data you want in the RAM. And you have to find this out by searching through the hac. In this case we are going to try to add 'Injector PulseWidth" to the '7747 datastream. A suitable address in the .bin could not really found, so we are going to get it directly from the register.

       LBC00     EQU     $BC00        ; DRP COUNT

      LBC0E     EQU     $BC0E        ; SYNC  BPW    PWM
       LBC14     EQU     $BC14        ; ASYNC BPW PWM

       LBC3C     EQU     $BC3C        ; PWM

So the next step is to decide which piece of data in the data stream we want to replace with the INJ PW. In this case PROM ID makes the most sense because it too is a 2byte value, and is hardly used.

        ;  ALDL XMIT TABLE OR ADDRESSE'S
        ; 127747 ECM
        ;
        ;  5.7L TBI    L05 C/K    87,91 TRUCKS
        ;
        ; DATA PIN: Read data on PIN "E" of ALDL Connector
        ;
        ; BAUD RATE:  160 Baud
        ;             Open         - 20 Bytes
        ;             10k          - 20 Bytes
        ;             Shorted     - 20 Bytes
        ;
        ;---------------------------------------------
        ORG $04E7    ;
LD4E7  FDB $D002   ; 1.  EPROM ID LSB
LD4E9   FDB $D003   ; 2.  EPROM ID MSB
                    ;---------------------------------
LD4EB   FDB $00FD   ; 3.  CURRENT IAC POSIT, (0-255)
                    ;      N = COUNTS

What we are going to do is change the .bin at L04E7 from $D002 to $BC0E and L04E9 from $D003 to $BC0F from above. Only we are going to do it with a constant so we can change it easily, without having to use the hexeditor.

So we make a XDF parameter as follows........


At this point we have just told the computer to look at a different address for the data to send out in the datastream.


Next step is to make a ADX parameter to view the data.


We make the packet offset 0x02, because I guess that is the spot in the datastream that should have what used to be PROM ID, should now be INJ PW.


Almost forgot, make the conversion as shown........



Now someone make a log and tell me it worked.......Please.