97 gmc jimmy won't auto. shift out of 1st?

[darry g]

will not automatically shift out of 1st gear, but I can manuelly shift it. any idea what i need to do to fix this problem?

 

[philip]

Try replacing transmission filter and fluid and check vacuum lines for breaks.

 

[Molson02536]

will not automatically shift out of 1st gear, but I can manuelly shift it. any idea what i need to do to fix this problem?

Transmission does not shift automatically, only manually. Swap in a known-good PCM, check wiring, check other sensors such as VSS and TPS, but before doing all that. Check the fuse to your transmission and if that is good and the rest of the fuses, follow with inspecting the wire harness which is located on the passenger side of the transmission.

Good luck and keep us posted, your transmission is electronically controlled to shift by the PCM.