This is what the end of the O2 sensor plug looks like for the Upstream. Does that look like what you have?

 

I have the check engine light on. I'm going to get my light and head up under the truck. Thanks again.

 

There is only 2 or 3 inches of wiring for this plug and it branches out of that large bundle of wires that is taped up right by the plug.. I was up under it again and can't find any harness with a male end that would plug in there...hmm Thank you for all the help.

 

Maybe it's a plug for the optional fog lights? I don't see on my harness where there's an unused plug wrapped up or anything

 

I'm going to search around for fog light hummer wiring to see if it brings anything up. My truck was a Canadian truck...maybe that's why it's different than yours... Thank you for all the responses. My Best.

 

You might also check if yours came equipped with a block heater. If so, you'll see it in place of one of the freeze plugs on either side of the block.

 

Not sure if this helps but I was looking at diagrams on the air suspension option. A Google search of where the relay is located resulted in the following:

"Along the left front inner frame rail towards the rear of the left front wheel opening"

sound familiar? If you don't have the air suspension, perhaps it used to and somebody deleted it?

 

I searched and saw this video on YouTube and thats exactly what it is. One less thing that i have to figure out about my recently aquired Hummer. Now i have to take a look to see if it was converted to coil springs OR he just removed the relay to keep it from lowering at 40mph etc. It has a nice ride height the way it sits

It is a fully loaded luxury edition. Now I know why the ride height button never did anything lol. Thank you so much for all your efforts. My Best.

 

All Figured out, good to hear!

if it was deleted and you're going to keep it that way, I'd use some electrical contact cleaner and clean that plug up really well then wrap it up and make it weather tight. You might use a simple test light and see if there's voltage to the plug with the key on. I suspect they probably pulled the fuse. Or .... maybe your air suspension is intact and maybe the relay got knocked off and all you need to do is replace the relay.

 

There is a fuse missing on the inside fusebox by the driver door. I forget what the description was as it was something I never heard of. I never had the dash warning lights on the second position. They would appear when you crank the truck to start then go out as normal. One day I popped the 10amp fuse in to see what would happen and the warning lights all came on with the key in second position. I also noticed I had to hold the brake pedal for the starter to turn so I figured maybe that's why the previous owner removed the fuse. Now I will check the pins on that relay holder by the front tire and see if this fuse might have something to do with it as well. It's the very top and very right side fuse in the corner. Then I will clean and watertight the connection. Awesome. Thank you again.