2003 Chevrolet 1500 - reduce engine power light won’t go off

i have a 03 chevrolet silverado ls 5.3 v 8 engine and i can not get the reduce engine power light to go off and the truck want but 10 miles and hour. can you please tell me what wrong wit the truck

Suggest you remove your phone number.
This will need the code numbers read to even begin diagnosising.
If your mechanic is not close by, have it towed.