Hey group I am brand new to Hummers and have a question. We just purchased a 2006 H3 last night and I am ordering a bunch of parts to slap on it before school starts.

I believe in fresh O2 sensors but when I roll under this one I am stumped. I see one way up near a heat shield and one way back under the 2nd row seat then I see a 3rd one on the down pipe that has no wire.

What am I missing?

 

Is there no way to edit a thread title?

 

Aftermarket exhaust? Post pictures. Btw, you only need 2, the upstream oxygen sensor is situated before the catalytic converter whereas the downstream oxygen sensor is located after the catalytic converter. The upstream sensor monitors the level of pollutants in the engine's exhaust and sends this information to the ECU that continuously adjusts the air-fuel ratio. The downstream sensor measures the level of pollutants passing through the catalytic converter. The information from the upstream and downstream sensors are compared by the ECU. If the readings from the two sensors become more similar to each other, the ECU triggers a catalyst inefficiency code.

 

Honestly I don't know enough to know if it has an aftermarket exhaust or not but it does not appear so.

There is one way high that gotes through a hole in the heat shield. It has a wire.

One about a foot down that has the wire cut off but it is clearly an 02 sensor screwed into a hole.

There is another behind the cat way back by the transfer case that has a wire.

We are not getting any check engine lights

 

Post a picture of your downstream sensors.

upstream here:

 

I am trying to get them from my phone to here.

I have that one then there is another just before that bend that has the wire cut.

The other one that is wired in is right behind the converter way back by the transfer case.

 

 

OEM, o2 sensor location(#2 & #5, L52vsLLR):

 

What I have looks like L52 with a plugged bung at #5 on LLR. What does that mean?

 

Getting back to your original post, Yes, fresh 02's does an engine good. Now that you know where the o2's are, just pull them, clean them, and reinstall with another dab of anti-seize(copper best for high heat application).
Also recommended by GM is top tier gas