1999 4.0L SOHC O2 sensor removal. | Ford Explorer Forums - Serious Explorations

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1999 4.0L SOHC O2 sensor removal.


New Member
March 4, 2011
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Okay i have been really frustrated by this. I have searched for a descent answer but now have come to this.
How do you remove and then attach the wires from the passenger side upstream o2 sensor on this engine? I can see it, but for the life of me cannot get anywhere near it to disconnect it. Its attached to the head at the rear between firewall. Please someone walk me through this because im going out of mind here.

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small hands

The photo below shows the two connectors mounted to the passenger side head.

If you have small hands you may be able to reach up thru the wheel well to disconnect the O2 connector. The photo below was taken during my engine removal after separating the engine from the transmission.

If you can't reach it from there removing the inspection plate under the carpet may provide access although I've never tried it.

I have tried the inspection plate thingy. lol no avail. As for small hands thats not happening either. Thanks for that response though and the great pics!

Just did it.

I can think of no way to show you via photo. So here we go, words aplenty.
The connector is a simple clip style connection. It is set up so that you may release the clip using a small flat screwdriver or an awl or anything similar.

I did it with the tire off. I removed the plastic wheel liner. Just to keep from suicide or heavy drinking. If you can now see the connector, the release clip is on the left side. It is facing you, so that if you poke it with a screwdriver or about a 6d nail or anything similar, it will depress the clip. You should be able to feel the spring action of the clip. If you are lucky and have done this with your left hand, your right can now pull gently on the wire, back towards the wheel area.

Mine had not been touched in 10 years, in Wisconsin salt etc., and it still released very easily. The female portion of the clip is pinned down very strongly. The male portion is the 02 sensor. If you threw a fit and gave it a violent tug, you might just get only the part you want in your hand. But I'd try this first.

I took a good look with a trouble light first. I saw the small rectangle opening on the left side of the plug. I have a long scratch rod tapered to a point, similar to an average nail. I poked that thing up in there into the rectangle opening and felt that great springy type release feeling. I then simply pulled towards myself on the wire and it slid out easily. Later I reinstalled it blind with my left hand also.

Very difficult to describe, but really easy once you know the location of the hole that lets you release the springy clip. It requires no force. A flat screwdriver that is really long also works great.

Hope this helps. It is difficult to describe but easy to do blind once you know the location and realize it is set up to just pull the wire towards yourself once the clip is released.