01 Tahoe taking off in 2nd and or 3 rd gear

I have a 01 tahoe that is taking of in 3rd gear. I have taken it to Amoco and High Tech Transmission and the transmission is fine. High Tech replaced the Harness and The seals and fluid. Amoco had it for 2 days and didnt find anything wrong they just reset the check engine light and it runs fine. So until the dealer can get me in Ill just keep unpluging the negitave battery cable for 5 min. which reset the computer and clears the check engine light and this cause it to run fine. Until the Check engine light comes on. Does anybody have a clue what this could be thanks.

I have a 01 tahoe that is taking of in 3rd gear. I have taken it to Amoco and High Tech Transmission and the transmission is fine. High Tech replaced the Harness and The seals and fluid. Amoco had it for 2 days and didnt find anything wrong they just reset the check engine light and it runs fine. So until the dealer can get me in Ill just keep unpluging the negitave battery cable for 5 min. which reset the computer and clears the check engine light and this cause it to run fine. Until the Check engine light comes on. Does anybody have a clue what this could be thanks.
i had this problem b4 it was the transmission valve body losing pressure