electrical gremlins and limp mode

[Perry Cole]

hey guys so i have a 1993 gmc sierra 4.3l long bed just got off trade. the guy i got it from said there's no 3rd or 4th but has 1st 2nd and reverse. i was thinking limp mode so i limped it home pulled codes and i have a code 43 and 28. along with limp mode i have some electrical issues as well and fixed some in the process. originally it had no speedometer or odometer no dash lights except check engine and check gauges and when you turn on the headlights the backlight of the a/c control unit shut off. the radio is out of it. so i started at the grounds i knew of the engine to junction block and junction block to body panel checked ground under dash where obd1 plug is it was good checked thermostat ground and they checked out ok found and extra ground strap on drivers side on trans case not sure where it goes so i was thinking pcm maybe? did research on that and replaced the drac and got the speedometer and odometer back but i got the wrong replacement pcm so waiting on that. am i missing any thing else?

 

[Schurkey]

43 is for the knock sensor system, including the harness and computer.

28 seems to be the trans range switch, including harness and computer.

Clear both, drive it, see what comes back.

Diagnostic procedure for both is in the service manual, which you need to have, or have access to. Some were posted as .pdf on this site, but I think the links quit working.

I get mine on eBay; or on DVD through Bishko, sold at Summit and other places. The DVDs work, but the paper manual is preferred.