Playing with the ECM

J.W. Harris jwharris at holli.com
Tue Dec 19 02:35:33 GMT 1995


>If someone like me, or you, or Hypertech, tries to gain access and change level
>three type of information in the new '97 VCM, and does not have the correct
>access code the FIRST TIME, the VCM will lock itself down into a
>non-functional unit that cannot be restarted except by engineers at Delco!!
>
Yes, I personally think OBDII is going to throw the aftermarket a really big 
curve.  Hacking into the box and reprogramming it is going to be harder 
still.  Removing the EEPROM and recalibrating it in such a way that no SES 
lights will be set will be even harder still.  I haven't heard anything 
about VCM's rendering themselvs useless with bad ClassII messages.  I think 
this one is wild speculation.  Any of you other Delco guys (or gals) care to 
comment?

On a lighter note at an SAE confrence on OBDII they were talking like 
manufacturers will be required to supply the hex scan codes for a particular 
parameters (TPS, etc.) right in the service manual.  It seems there is 
supposed to be a low cost "minimum function" scan tool that doesn't have 
them programmed in already.  The technician will have to enter the hex bytes 
by hand and the manual will tell how to interpret the response message.  
Tedious, but if it's true, a gold mine for you guys who want to make your 
own scan tools.  Anybody seen this in a '96 manual?  In the long run this 
stuff (Class II messages) will all probably become standard and public 
domain.  Except for the securtiy algorithms to unlock the box and reprogram, 
do device control, etc.  We can only hope.
----------------------------------------------------------------------------
J.W. Harris                                          Delco Electronics Corp.
Project Engineer                                     One Corporate Center
Powertrain Electronics                               M.S. CT40C
                                                     Kokomo, IN 46904-9005
jwharris at kocrsv01.delcoelect.com

Of course, all responses are my own and should not be mistaken for those of
Delco Electronics or General Motors.




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