Mechanics

BANK 1, SENSOR 1 OXYGEN SENSOR

1999 Ford Explorer

Engine Performance problem
1999 Ford Explorer 6 cyl Four Wheel Drive Automatic 174000 miles

My check engine light just recently came on. I ran the codes and it turns out to be my O2 Sensor (Bank 1, Sensor 1). I have a 1999 Ford Explorer with a 4.0 SOHC. Is this sensor located on the passenger side of the vehicle in front of the converter? And if so, can this be changed without having the car on a lift? Thank you.
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Fender1
February 20, 2009.



You are correct with the location of the o2 sensor.

It should be easy to get to it if you can get under the vehicle.

Blackop555
Feb 22, 2009.
Thank you for your response. I was able to slide under the Explorer relatively easy and found the sensor without any problems. What should have been a 20 minute job turned into almost 2 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 12 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!

Tiny
Fender1
Feb 23, 2009.
Yeah im not a bigfan of that set up. But they do prevent the wires from melting on the hot exhaust!

I hope you put antiseize compound on the threads, that way it wont seize up on you.

Lots cut the sensors wiring harness and splice in the new one, but unless you solder it and heatshrink it it will rust and mess with the sensor readings.

Also examine the old o2 sensor for signs of damage or white/green flaky stuff for indications of why it went out.

Blackop555
Feb 23, 2009.
Luckily the new sensor that I bought (from Ford) came with the antiseize on the threads.

The old sensor didn't 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 at the dealer for a new sensor just seemed to be the way to go. Hopefully the other 3 don't go out anytime soon, especially with each sensor costing that much.

Tiny
Fender1
Feb 24, 2009.
If that sensor was missreading even due to old age it might not have thrown a lean code.

And it could have been robbing you of precious gas mileage. Replacing it at 100 for the part could easily save you more then that if it was missreading and hampering your performance.

That was a smart move!

Blackop555
Feb 24, 2009.
It's funny that you mention that the sensor could have been robbing me of gas mileage. Since I've replaced the sensor this past weekend, I'm getting MUCH better gas mileage. I would normally get 300 miles to a tank of gas. I'm now going on 350 and still have a 1/4 tank left. I'm guessing that the sensor had probabaly gone bad long before I realized it. I wonder if replacing the other 3 would make any more of difference?

Tiny
Fender1
Feb 25, 2009.
Its a gamble. It wouldnt hurt to replace them with the age, just replace the bank 2 sensor one. Dont worry about the bank 1 and bank 2 sensor twos, the ones after the convertors.

All they are for is monitoring the catalytic convertor to tell if that is still working or not. Has nothing to do with gas mixture

Blackop555
Feb 25, 2009.
I have a 1999 Ford Explorer with 178,000 miles. 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?

Tiny
Fender1
May 27, 2009.