Role of O2 sensor 1996 2.4

My O2 sensor studs recently rusted away and the whole unit is just hanging in the air by the wires. It is, of course, kind of loud right now...but, otherwise the truck seems to run just like it always did. Not even a CEL.

Now, I guess I thought the O2 sensor provided one of data streams for the engine management. But, now, I wonder what it's actually doing.

Roy

 

Your check engine light bulb lights up with the ignition switch in the on position??

Yes indeed it should trip a code

It might be a two trip code to cause the light to light.

Don`t leave it hang you will be fixing wires as well

 

Is there just one post cat sensor on a 96?

 

This is a nice description of the O2 sensor function:

http://www.autotap.com/techlibrary/understanding_oxygen_sensors.asp

Copy...not letting it hang any more.

It fell out while driving, I went another couple miles, was out of the truck all day, drove it home...6 miles.

This is the one bolted into the downpipe...before the cat.

I will check for a CEL-at-start tomorrow.

I suspect no one will be able to say what the impact on MPG would be without the sensor installed.

Thanks for the responses.

 

Yup...as predicted, the CEL has come on.

 

Which sensor was it? Before or after the catalytic converter? If it's the post cat sensor then it's only job is to monitor catalyst efficiency. It has no impact on fuel trims\maps. That's all done by the front O2 sensor, before the cat.

Edit: nvm, but the info is still relevant.

 

My 96 3RZ had pre and post sensors

 

That thing will be "reading" a bunch of fresh air hanging out like that. Expect fuel mileage to suffer

 

See post 4

 

Ah shit, guess I skipped over that statement. My bad.

 

I feel bad for these salt belt guys.. sensors falling out?!? Wtf

 

Makes sense.

96 was a transition year to OBDII for most marques.

The post cat sensor was pretty much just to indicate if the cat had failed.

 

You have no idea my new steel on the rack inside rusts just from the damp climate

 

I went ahead and reinstalled the sensor. Turns out, both nuts rusted off and one of the studs is considerably shorter than it once was.

It was the front one...on an OBDII, 2.4, litre I4.

Maine is terrible for rust. There are guys replacing brake lines on three year old trucks!

 

In the unlikely event that someone is interested, the studs are M8 with 1.25 pitch.

I had to delete the gasket due to the rusted-short stud. I did a form-in-place gasket replacement with Permatex muffler sealant. Seems, all is good.

https://www.permatex.com/products/s...stem-repair/permatex-muffler-tailpipe-sealer/

Thanks again,

Roy