SUMMARY: CTS & IAT pullup

[Gregory A. Parmer]

There was a recent flare of info/questions about
the pullup resistors used in the Delco
ECMs for reading CTS, IAT, MAT, and etc.

The 2 Delco ECMs I have do CTS 2 different ways,
hence the varied list opinions. The '7783 is for a 
V6 SFI similar to the '7148.  The 2 seem to typify 
other units.

 '7783 -- switched 4k and 350ohm pullups on CTS (c10) 
 '7783 -- 2.5k pullup on MAT (c11)

 '7747 -- 1k pullup on CTS (c10) 
 '7747 -- (no IAT or MAT used)

The switched method was used on CTS for the '7783
(to achieve better accuracy around operating temps?):  
      ----------------------------- +5
      |                   |
      \                   \
      / 3.6k               \     software controlled
      \                     \     switch
      /                   o  \
      \                   |
      |                   |
      |----------------------------/\/\/\----o to A/D, etc.
      |                              10k
      /
      \
      /
      \ 348
      /
      \
      |
      |
      o  terminal on ecm (c10 CTS)

Non-switched MAT for '7783:
      ----------------------------- +5
      /
      \
      /
      \ 2.5k 
      /    
      \
      |
      |-----/\/\/\--o   A/D, etc
      |       10k
      |
      |
      |
      |  
      o  terminal on ecm (C11 MAT)

Non-switched method CTS for the '7747:
      ----------------------------- +5
      /
      \
      /
      \ 1k 
      /    
      \
      |
      |-----/\/\/\--o   A/D, etc
      |       10k
      |
      |
      |
      |  
      o  terminal on ecm (C10 CTS)


See
   http://www.acesag.auburn.edu/~gparmer/efi/inside7747.htm
for actual shots of the involved components (I coulda missed
something at the other end of a trace, but I doubt it).

Thanks Peter, Tom, Bruce, and others who contributed/prodded. :)
-greg