7730 Vss signal processing

[Fisystems at aol.com]

Try 

http://www.cis.udel.edu/~davis/z28/ECMs/86to92.txt

 <A HREF="http://www.cis.udel.edu/~davis/z28/ECMs/86to92.txt">
http://www.cis.udel.edu/~davis/z28/ECMs/86to92.txt</A> 




In a message dated 5/7/01 11:27:50 PM Eastern Daylight Time, 
karljiml at compuserve.com writes:

<< I think I've learned that the 7730 ECM, depending on the car in which it 
is 
 installed, handles the Vss signal two ways:
 
 A) Raw Vss signal from transmission sensor input on pins B9 & B10, and 
 outputs signals for 4000p/mi on pin B11and a 2000 p/mi  on pin C1
    OR
 B) Accepts a 4000 p/mi signal from an external signal buffer (yellow box) 
 on pin C6
 
  From experience, if the MEMCAL is expecting option B, but the car is wired 
 for option A, a digital speedometer reads much higher than actual speed.
 
 Question: Has anyone found the locations in the MEMCAL that control how the 
 ECM handles the Vss signal. I want to change transmission Vss sensors, but 
 it looks like I will need to hack the MEMCAL to make it all work. I need to 
 decide if I should even attempt it, or leave it alone.  Changing the MEMCAL 
 to one from a different vehicle is not an option; too many other vehicle 
 specific parameters would be affected. I have the capability to read, edit 
 and burn a MEMCAL, but have no experience disassembling the code. I don't 
 expect anyone to "do the mod for me," but was sure hoping not to have to 
 reinvent the wheel. >>
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