SES Light/ 02 Sensors

[Chode]

Hey guys,Had a question and thought maybe someone could help.Here it goes,
My ses light came on and I had the local auto parts scan the codes and they told my it was the 02 sensors all 4 of them, well since it is a 2000 with 150+ miles on it i figured why not so I changed all 4 out had the light reset was ok for 2 days and bam its back on throwing the same codes.What gives I spent like 400 bucks for those things anyhow I will stop ranting now but if any one has had similar experince like this please let me know before I take it to the shop.

Thanks in advance....

[Old Diesel]

The parts stores can only tell you what the computer tells them. When your o2 sensors go bad (all 4 at once) that indicates that there is something else going on with the truck. The computer may not have a code for what is happening, and thus won't recognise any problem until a known parameter is read and found to be out of whack. Sure, there is a possibility that you got four faulty o2 sensors, but I would try to get it in and have a dealer scan it. Maybe if you live near someone with ls1 edit or AutoTap they could hook it up and see what the computer is seeing, but my guess is that there is something else in the emissions system not doing it's job. If you talk to a good mechanic, they'll tell you that the computer codes will only give you a starting point to diagnose the problem. You start with the o2 sensor and move up the diagnostic tree following all of the little branches until you find what the root cause of the problem is. If you get a hold of a service manual, it'll tell you how to test your o2 sensors, and what to look for if they check out okay, and so on. Good Luck!