Oxygen sensor locations?

Thank you for your response. I was able to slide under the vehicle relatively easy and found the sensor without any problems. What should have been a twenty minute job turned into almost two hours. Getting to the O2 sensor and putting a short 7/8 Inch wrench on it was the easy part. It was the wiring harness that was located the full length of the wiring harness straight up and between the bell housing and the body. I was finally able to reach it using a twelve inch thin screwdriver to depress the harness clip and gently pull the wires down.

Putting the new clip in was the easy part?

Thanks again!

Luckily the new sensor that I bought (from Ford) came with the anti-seize on the threads.

The old sensor did not look too bad when I removed it. The code indicated that the heating element inside of the sensor had gone bad. I had read that sometimes people had luck by just pulling the harness and then reinserting, but with 174,000 on the car and this being the original sensor, spending $110.00 at the dealer for a new sensor just seemed to be the way to go. Hopefully the other three do not go out anytime soon, especially with each sensor costing that much.

It is funny that you mention that the sensor could have been robbing me of gas mileage. Since I have replaced the sensor this past weekend, I am getting much better gas mileage. I would normally get three hundred miles to a tank of gas. I am now going on three hundred and fifty and still have a quarter tank left. I am guessing that the sensor had probably gone bad long before I realized it. I wonder if replacing the other three would make any more of difference?

Just recently there appears to be a whining/whirling noise coming from underneath while in drive. It occurs when in drive and not moving and gets worse/louder when pressing the gas. I had the transmission rebuilt at 120,000. Any thoughts on what this could be?

1997 Ford Explorer V8 all wheel drive automatic.

Is the 02 sensor bank 2 down stream located on the right or left side?

Okay, my SUV has been running to lean for the longest time. I have had it tested for codes and it keeps saying bank 1 sensor 2. Well I replaced that one and replaced bank 2 sensor 1 also because I was told it was going bad. My engine still runs too lean. While doing an oil change I noticed bank 1 sensor 1 o2 sensor was not plugged in. I figured this is where the problem is. Now I cannot find the wire to plug the sensor back in. I have looking under the motor where the sensor is and up top under the master cylinder and brake booster and I still cannot find the other end to plug the sensor back in. If anyone knows where the wire is please let me know. By the way, my engine is the OHV 4.0 if this helps.

Looking for upstream O2 sensors for the Explorer it is an 4.0L EFI OHV engine, thanks.

Do you have a diagram of where they are all at? Thanks.

Okay, thanks I found them. Also, is it possible for the SUV to have its fuel trims at -100 running rich, but have a check engine light p0171 as it is lean?

Was running fine about a week ago, with gas slowly going away, but now it came with codes p0171, p0302, p1131 and my gas is going by incredibly fast.

I have a 1999 Ford Explorer 4x4, 115,000 4.0L V6.
The check engine light is on, the test was performed at our local auto store showing the oxygen sensor needs to be replaced. I am looking for any information on how to replace this ourselves. I have searched the many sites and seen that there are possibly two that needs to be replaced as well, as I was under the assumption that there was only one. But I have not found any information that states exactly where they are located and the easiest way to go about changing them. Or if it is better to take it to an auto shop and pay them to do it? Any help would greatly appreciated.