1999 Slt

Well Here it gose again. About the end of june the fuel pump went out. Got a new one, seemed to be good after that. We only drive the truck on weekends since gas went out the roof. My wife tried to drive it last Sunday. She said it ran fine then started to run rough, and the Check engine light came on. I started it on Monday, seems to idle fine but the light is on. I seen something on here about the codes being on the OD? Is there something I can look for before hauling it off to a garge? I know it just went over 70,000. The last time I drove it, it ran good as new. Any help.........

bring to your local parts store (advance auto, autozone...) and have them read the code.
If it is not shifting or shifting at the wrong time and/or speedo doesn't work, it is probably the differential speed sensor. Easy to replace, but only available from the dealer.

Turned out to be the Oyxgen sensor, I replaced it 3 times and the light wont go away. It runs fine, just the light comes back on. Any other ideals????????

Did you take it back and have it read again? Sometimes that will clear it. If not, it may be a broken or coroded wire.

Every time I changed the O2 sensor They cleared the code. The last time I replaced it, I made it 4 blocks till the light came on. Same code, shows heater failer.