Bank 1, sensor 1 oxygen sensor location

Tiny
FENDER1
  • MEMBER
  • 1999 FORD EXPLORER
Six cylinder four wheel drive automatic 174,000 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 the 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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Friday, February 20th, 2009 AT 8:43 AM

24 Replies

Tiny
BLACKOP555
  • EXPERT
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.
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Sunday, February 22nd, 2009 AT 4:22 PM
Tiny
FENDER1
  • MEMBER
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!
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Monday, February 23rd, 2009 AT 10:23 AM
Tiny
BLACKOP555
  • EXPERT
Yeah, I am not a big fan of that set up. But they do prevent the wires from melting on the hot exhaust!

I hope you put anti-seize compound on the threads, that way it will not seize up on you.

A lot of people cut the sensors wiring harness and splice in the new one, but unless you solder it and heat shrink 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.
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Monday, February 23rd, 2009 AT 10:22 PM
Tiny
FENDER1
  • MEMBER
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.
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Tuesday, February 24th, 2009 AT 8:16 AM
Tiny
BLACKOP555
  • EXPERT
If that sensor was misreading even due to old age it might not have thrown a lean code.

Also, it could have been robbing you of precious gas mileage. Replacing it at $110.00 for the part could easily save you more then that if it was misreading and hampering your performance.

That was a smart move!
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Tuesday, February 24th, 2009 AT 9:42 PM
Tiny
FENDER1
  • MEMBER
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?
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Wednesday, February 25th, 2009 AT 9:14 AM
Tiny
BLACKOP555
  • EXPERT
It is a gamble. It would not hurt to replace them with the age, just replace the bank 2 sensor one. Do not worry about the bank 1 and bank 2 sensor twos, the ones after the converters. All they are for is monitoring the catalytic converter to tell if that is still working or not it has nothing to do with gas mixture.
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Wednesday, February 25th, 2009 AT 6:38 PM
Tiny
FENDER1
  • MEMBER
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?
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Wednesday, May 27th, 2009 AT 8:19 PM
Tiny
ALLEN45
  • MEMBER
  • 1997 FORD EXPLORER
1997 Ford Explorer V8 all wheel drive automatic.

Is the 02 sensor bank 2 down stream located on the right or left side?
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Wednesday, September 19th, 2018 AT 12:20 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
I have attached a diagram below of the Oxygen Sensor locations for you truck.

Let us know if you need anything else.
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Wednesday, September 19th, 2018 AT 12:20 PM (Merged)
Tiny
TREYEXPLORER
  • MEMBER
  • 1997 FORD EXPLORER
  • 4.0L
  • V6
  • 2WD
  • AUTOMATIC
  • 230,000 MILES
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.
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Wednesday, September 19th, 2018 AT 12:20 PM (Merged)
Tiny
BMDOUBLE
  • EXPERT
When it comes to sensors, especially oxygen sensors they are telling you what is going on with the fuel/air ratio, by giving you a lean code does not mean sensor failure. Do not shoot the messenger in other words and do not let a parts store tell you what you need. The most common failure in these is either the intake seals or PCV hoses. Spray a little water over the intake and listen for a slurping sound.
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Wednesday, September 19th, 2018 AT 12:20 PM (Merged)
Tiny
OHYEA
  • MEMBER
  • 1998 FORD EXPLORER
  • 4.0L
  • V6
  • RWD
  • AUTOMATIC
  • 206,000 MILES
Looking for upstream O2 sensors for the Explorer it is an 4.0L EFI OHV engine, thanks.
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Wednesday, September 19th, 2018 AT 12:20 PM (Merged)
Tiny
HMAC300
  • EXPERT
Should be before converters.
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Wednesday, September 19th, 2018 AT 12:20 PM (Merged)
Tiny
OHYEA
  • MEMBER
Do you have a diagram of where they are all at? Thanks.
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Wednesday, September 19th, 2018 AT 12:20 PM (Merged)
Tiny
HMAC300
  • EXPERT
No, I checked in our manual and they just said location. All you have to do is follow exhaust manifolds down to converter. There are two before and two after converters.
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Wednesday, September 19th, 2018 AT 12:20 PM (Merged)
Tiny
OHYEA
  • MEMBER
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?
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Wednesday, September 19th, 2018 AT 12:20 PM (Merged)
Tiny
OHYEA
  • MEMBER
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.
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Wednesday, September 19th, 2018 AT 12:20 PM (Merged)
Tiny
HMAC300
  • EXPERT
171 is running lean and 302 is misfire on number two cylinder both of these can be caused by low fuel pressure. 1131 can be caused by the items in picture which includes fuel pressure which should be 30-45 psi. Auto parts rent gauge. If pressure is okay then I would suggest having a pro diagnose this as it is extremely hard to find cause of misfires.
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Wednesday, September 19th, 2018 AT 12:20 PM (Merged)
Tiny
MDGONNAB
  • MEMBER
  • 1999 FORD EXPLORER
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.
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Wednesday, September 19th, 2018 AT 12:20 PM (Merged)

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