Can someone explain why no wiring has to be changed doing a OBD1 conversion when 96-97 PCMs use PCM pin D7 and pin 2 on the OBD2 ALDL for the serial data and the 94-95 PCMs use PCM pin D30 and ALDL pin 9 (95s) for the serial data? Is it because GM left the ALDL 9 to D30 wire in the harness on the 96, 97 cars and just added the ALDL 2 to D7 wire.

http://shbox.com/1/1995_pcm_conn_d.jpg

 

PCM C4 pin 30 to DLC pin 9 is still present with OBD-II.