How to Replace Upstream O2 Oxygen Sensor 2004-07 Toyota Highlander L4 2-4L

Hi. I'm Mike from 1AAuto. We've been selling auto parts for over 30 years!

The front O2 sensor is located here before the cat and the wire for the connector followed up here to the side of the engine. We've removed the engine cover. You could do this without removing the engine cover. This just makes it easier to see.

It is clipped to the radiator hose. We'll squeeze these tabs. Just using a flat bladed screwdriver, try to pry this apart. It's kind of stuck. Usually, these come apart pretty easily. So I'll squeeze the two tabs together and then pry it on this. Squeeze them together. We'll keep prying. That will come apart. You can see how it works. So it clips together and you just squeeze these tabs together. It's just filled with dirt. It's hard to get apart. Put that aside to reuse it.

You need to unlock the O2 sensor connector up here. So you can either push in on this lock. See, it's going to move that tab up. You might not move it up enough. Take a small flat bladed screwdriver. Sort of pry it up and at the same time, pull the connector out just like that.

Our oxygen sensor socket is too wide to fit in this shielded oxygen sensor. You can get a thin walled oxygen sensor socket if you need to remove this oxygen sensor and reuse it if you are replacing the cat. I plan on using the same size socket but in a thin walled, just a regular version. However, the wires are in the way. So again, if you want to reuse your O2 sensor, this would not be the way to remove it, but if you need to just get it out because it's failed and you got to replace it with a new one, you can do this. So I'm going to cut the wires. Take that harness out of there. I'm using a 7/8” extra deep socket and a breaker bar. Put into place. Break it free. Spin it out. You can see this had a shield on it.

Here's the original O2 sensor. Had a shield on it. There's a brand new one from 1AAuto.com. Doesn't have a shield on it. Not a big deal. You don't 100% need that. Obviously, I cut this to get it off. The harness is the same length with the same style connector. This'll thread right in and work great for us. So it already comes with anti-seize applied to the threads.

Thread it in by hand. Now we can use our actual oxygen sensor socket and I will tighten it down. Basically, just feel the crush ring that's on the end of it. It'll start to crush and right there, that's perfect.

Run the wire back up underneath the upper radiator hose. Then well plug the connector back in. That's keyed. It can only go in one way. I'm going to hold it from the back. It'll click when it locks into place. Take our little wire holder. Get the wire up and away from the exhaust and just clip it in place just like the original. The O2 sensor's replaced.

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