hey just looking for a little diagnotsic help here, the transmission is an 07 4l60e, in a gmc sierra 4.8L, basicly it ran fine then was parked for about a year, and now it isn't shifting right. it starts in 2nd gear and stays there when its in the drive range, it has manual first, manual second and reverse, initially it set the mil and the digital shift indicator in the dash disappeared , and had 2 codes p0700 and p1815, so i replaced the neutral safety switch and the valve body pressure switch assembly, reset the computer

after that and the reset the indicator started working again and no code so i test drove it and same problem after i shut it off and turned it back on again, no shift indicator in the dash any more, and now no codes, did i mention it only has 20k on it, and the pan was crystal clean... like new, no sediment even. lol im pulling my hair out.

p.s. also tried pulling battery and wiring harness to TCM and ECU to check for moisture issue and re plugging they looked clean and brand new, no signs of moisture. has anyone experienced an issue like this this before?

 

As per the rules since this is not thirdgen camaro/firebird related I have to close this. Please PM me or JT if you have any questions.