My wife's truck is a '00 Vortec 5.3 C1500, it just turned 100K.
Almost like clockwork, the "service engine soon" light came on.
I keep it maintained well, very good emissions still, always gets warmed up, runs perfect, get's good gas mileage, yada, yada, yada.
Basically what could I be in for at the dealer? O2 sensor maybe?
Brian
Go to autozone get the code scanned, DON'T BUY ANYTHING, and tell me what it is.