chevy s10 check engine light and shifting prob

[gunner10]

have a 1997 chevy s10 4x4 auto tranny .the check engine light has come on twice in about a 3 week period and each time the rpms were jumping up and staying when the gas was pressed and truck in neutral, and the truck shifts hard from 1 to 2nd when driving. no noises or clunks or chunks just a hard shift this hard shifting decreases the more the truck warms up and eventually is smooth with no problems the rpms also return to normal after warmup but the check engine light stays on. have checked fluid level and its fine this has only happened twice but each time the temperature has been about 35 degrees or colder any ideas or thoughts or something ive missed would be appreciated thanks!

[busa_4]

go to pepboys or aotuzone and have the codes scanned. according to everyone on here they will scan it for free. come back here and give us the code/s and definition.

[BlazerLT]

Get the codes scanned.