How long do you have to keep the batteries disconnected  to drain the computer, in order to reboot?

  I need it to be rebooted so that it will shift out of 1st gear (automatic trans) without removing the relay & manually shifting only giving me 2nd, & 3rd gears. 

Edited May 30, 20195 yr by Rayce
Spelling glitch

You could leave unplugged for a mont and it is still going boot up like it always does at key on. Sounds like you have a problem somewhere else. But I dont know auto trannys at all.

That's likely not a computer issue, but a trans issue.

Draining all the power out of the system is as simple as removing ALL 4 battery main wires from the battery terminals BEFORE touching the negative and positive main wires together on each side.  It will complete a circuit without the batteries in the loop and use up the rest of the power in the system.  DO NOT do one at a time or you will fry some stuff and have 2 problems on your hands.  

 

With that said I agree with the previous posters...sounds like you have a transmission problem that draining your system of electricity will not help.