Playing with the ECM

[Daniel R Burk]

>
>Markus Strobl <eusmsrt at exu.ericsson.se> has written:
>
><snip>
>
>> Second subject: I own a '96 Camaro with the LT1. The service manual I
>> read was for a friends '95. GM did alot of changes for '96 to 
>> comply with OBDII. My owners manual says that the ECM now detects
>> misfires, and will flash the service engine light if it detects a
>> misfire. The '96 also has 4 (!) O2 sensors (dual cat), to detect
>> catcon degradation. 
>
>> Does anyone have any info on OBDII? Ie how much can the engine be
>> modified before the ECM tilts? Can the ECM be modified, or can
>> it be fooled be changing the sensor readings? Any info appreciated.
>
><snip>

Marcus:  Before you modify your ECM let me tell you about a little conversation
I have had with a GM engineer who actually worked in ECM design.

GM will be designing their new vcm (vehicle control module) with anti-tampering
software.  There are three levels of information available on the new vcm:
        1) general engine diagnostics (freely available to scan tools)
        2) dealership functions (like clearing the trouble codes)
        3) emissions functions ( fuel maps, shift maps, ignition timing)

As you can guess, level two will be only available to authorized service
personnel.  Level three will be protected from modifications from everyone
except GM.  

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!!

Yup, it sucks don't it?  

I asked the engineer "Why!?"  and he replied it is because of liability
concerns that GM is implementing this type of security.  

--- Thought you would like to know that I am going to buy me a used '95 or '96
in a few years.  I don't want the '97 anymore.

---Dan