I am posting this to all as it affects a lot of GM vehicles but this answers 96 s10 Starter specifically.
The Power Relay System was designed to help eliminate DTC 66, 67, 81,82 and
83 on 1995-up General Motor trucks or DTC PO740, PO785, PO758 and PI1860 on 1996-up GM trucks and 1998-up S10 and Bravada. Many times these codes are set because the ignition switch fails to supply enough voltage to the transmission through the ignition circuit, just after start up.Once the ignition switch fails to provide adequate voltage to the solenoids, the feedback to the computer trips any combination or all of the above codes. You can replace the ignition switchas as a temporary fix or you can install the Power Relay System and fix the problem. It is 4 wires. The kit costs under $100 retail and is posted on the TRN (Transmission Rebuilders Website). It is also available from the major transmission parts distributors. I will try to have one posted to Ebay as soon as I can I can arrange to get you one just send me an email but do not expect an answer before the 25th. . Bill