Originally Posted by
NomakeWan
GRAY Connector
C1 Ground
C11 Ground (when key is inserted into cylinder)
GREEN Connector
E4 & E5 +12V (when key is turned to run position)
E12 to F5 PASSkey Resistor Value (VATS)
F1 +12V
F12 ALDL
You were able to get your CCM downloaded, so I assume you have an ALDL cable you can use to talk to the CCM. Just connect the ground from your cable to the same ground as pin C1, and connect the ALDL data pin to pin F12. ALDL does RX and TX on one pin.
EDIT: It occurs to me that you should probably confirm those pinouts with an FSM for 1990 first. I don't have the electrical supplement for 1990 so I can't confirm that for you. The above pinout is correct for the 1994-1996 CCM.