5.3L O2 Sensors

[roadmaven]

Here's the scoop. This past weekend we took our Envoy XUV (5.3L) on a trip out on Route 66 through Missouri with our trailer. I have a Scan Gauge II that I had hooked up for the whole trip. CEL popped on, checked the Scan Gauge and it read a P0134 at first. Then after I cleared it, the CEL came back on and this time it read a P1133. The Envoy has 122K miles on it and since we've had it just a year, I don't know if the O2 sensors have ever been changed. After some research, the likely culprit is the upstream sensor. However, I just need to verify, are there one or two upstream sensors on a 5.3? I've seen some things that suggest there are two...or is there just one?

 

[jimmyjam]

yup theres two upstream two downstream

 

[roadmaven]

Thanks! Probably best to change them both, or does either code distinguish which one is having an issue?

 

[jimmyjam]

both codes point to bank 1 sensor 1 which would be driver side pre-cat

don't forget to inspect the wiring/connector first, might be something simple.

 

[RayVoy]

Thanks! Probably best to change them both,

You'll find the occasional reference that O2 sensors will start to get lazy around 80,000 miles. and you will also find info that contradicts that. I don't know which is right.

Years ago, when manufacturers decided plugs should be changed at 100k, I decided that was also a good time to change the O2 sensor(s). I just change the front ones, I don't care if the rear ones get lazy, they won't impact gas mileage. I also try to ensure they are the same. Sensors from one manufacturer may respond a little different than those from an other manufacturer; although, still within specs.