4L60 won't shift out of 1st

[Griztek]

This got posted in the Blazer forum somehow(my bad) so I'm moving it to here.

Ok, I'm tired of reading trying to find an answer to this question....

Looked at a 2000 Sonoma 4x4 auto. The truck had been sitting for a year only being driven a few times. It made a 350 mile trip (after adding a bit of tranny fluid) to it's current location and worked fine. Been sitting for sale since July.
Took it for a test drive and it won't shift out of 1st gear on it's own. Manually shift into 2nd and it will go into 2nd, but any other position drops it back to 1st. Reverse is fine.
REading other posts has me thinking electrical connection issue, but it's a shot in the dark. ANYONE??????

Update today12/5: Got the scanner on this truck finally and got a low speed sensor voltage code, PO502. This makes sense to me as to how this can cause issues. Question of the hour ......

Will a faulty speed sensor cause this problem? (keep the tranny from shifting)

[MT-2500]

Originally Posted by Griztek

This got posted in the Blazer forum somehow(my bad) so I'm moving it to here.

Ok, I'm tired of reading trying to find an answer to this question....

Looked at a 2000 Sonoma 4x4 auto. The truck had been sitting for a year only being driven a few times. It made a 350 mile trip (after adding a bit of tranny fluid) to it's current location and worked fine. Been sitting for sale since July.
Took it for a test drive and it won't shift out of 1st gear on it's own. Manually shift into 2nd and it will go into 2nd, but any other position drops it back to 1st. Reverse is fine.
REading other posts has me thinking electrical connection issue, but it's a shot in the dark. ANYONE??????

Update today12/5: Got the scanner on this truck finally and got a low speed sensor voltage code, PO502. This makes sense to me as to how this can cause issues. Question of the hour ......

Will a faulty speed sensor cause this problem? (keep the tranny from shifting)

Check you first post .
You have a answer there.