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Bank 1, Sensor 1 (upstream, firewall) O2 replacement

Ray

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Jul 10, 2001
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Humble
Here is the O2 sensor replacement written by GoldenTour. Download at your leisure!
 

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  • Bank 1 Sensor 1 O2 replacement.pdf
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BrApple

No Life But CEG
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another way to do it is to get the proper sized wrench and cut it down so that it will fit in the space available and you can get to the sensor from under the car
 

2X95SEs

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Oct 27, 2000
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Location
Houston, Texas
Check your rear mount - roll restrictor - to see if it's broken. When it breaks the engine will be closer to the firewall and make it harder to reach the O2 sensor.
 

MaddMike2

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Jul 8, 2005
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Location
Ohio
another way to do it is to get the proper sized wrench and cut it down so that it will fit in the space available and you can get to the sensor from under the car

If you do not want to cut a wrench, Sears has a short box end 22mm. that is what I used.
 

Desiato

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Ottawa, ON
I started this today on my 95LX/V6/Auto, but unfortunately my hand is unable to fit under the wiring harness. My wiring harness did not have a lot of room to maneuver, however I was able to move it as far as is indicated in the pictures. Being a delicate 95 harness, I don't want to force it more than I already have.

I'm going to have my girlfriend reach in and attach the o2 socket and then screw in the new o2 sensor tomorrow morning. :)

Update: All done. I was able to contort my hand in with a lot of effort and finish this. Thanks to GoldenTour and the CEG.
 
Last edited:
Joined
May 15, 2007
Messages
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Location
Clifton, NJ
I would have to say this was the hardest job I ever did!!!
However, (Post #1) Great How to, it'll help out a lot of people who wants to do it themself!!!

Will
 

Tony2005

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Jun 18, 2005
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Does the Contour only have the one O2 sensor?
......
...
1995 4 cylinder, 1 Upper O2 sensor.
1996 onwards 4 cylinder, 1 Upper and 1 Lower
1995 6 cylinder, 1 Upper Bank 1 and 1 Upper Bank 2
1996 onwards 6 cylinder, 1 Upper and 1 Lower Bank 1; 1 Upper and 1 Lower Bank 2.
 

01Roush

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Aug 2, 2007
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Just did this last night on my CSVT. Good write up, but still a PITA. Rent the 02 Sensor kit from Autozone, it's alot of help.
 

GoldnTour

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Dec 15, 2005
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Glad it helped. I wasnt smart enough into looking into a rental kit. What was in the Kit? different sized sockets?
 

01Roush

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Aug 2, 2007
Messages
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yes, 2 crow-foot sockets (I think that's what they're called) that allow for alot more room to manuver a ratchet, as opposed to using a traditional O2 socket and wrench. it worked great.
 

SVT_Fan

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Sep 3, 2007
Messages
59
Location
Canton, MI
Great write-up

Great write-up

I recently swapped out the same O2 sensor on my CSVT and found the instructions spot on. I did however find that an offset O2 sensor wrench was a bit easier for me to manuever, but nonetheless ---- the write up was very very helpful. Thx!
 

CSVT_2004

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Location
Wisconsin
Like the write up!

Like the write up!

I may have to replace my upstream sensor soon, but I'm not sure yet... The CEL has come on twice in three days with P0420 bank 1 lean, and usually it goes away for like 5 or 6 months at a time, but i'm thinking the sensor is finally starting to go, (105,000+ mi) but idk, just have to wait an see if she throws another one in the coming week. If she does, I suppose it could be a project for the meet on the 6th.
 

Recoveryone

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this info saved me a big headache and time concering those codes

8)Clear Codes/Reset PCM by removing Fuses 4 and 11 for 10 minutes.
Some CEL codes that may give you the impression that this particular sensor needs to be replaced:
P0133-â​
oeHeated upstream 02 sensor circuit slow response (bank 1)â
P0171-â
oeâ •System too Leanâ • (bank 1)
P0172-â
•System to Richâ • (bank 1)
P1131-â
oeLack of upstream heated oxygen sensor switch-Sensor indicates Lean (bank 1)â
P1132-â
oeLack of upstream heated oxygen sensor switch- Sensor indicates Rich (bank 1)â
**Would like to thank â
oeWilliamâ • and â oeannakobyâ • for past threads that made some of this information
possible, written by â
oemycainsbrokenâ •**

**Pictures and Updates by Crystian C. (Golden Tour) 8/11/05**
 

Spikedog

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Oct 17, 2007
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Location
Wyoming
Big thanks

Big thanks

I just did this job last night. 2 hours to get it done. I'd changed the other 3 sensors last month, and had written that sensor off as impossible to change. The writeup was very helpful.

One comment - the wiring harness wouldn't move more than a 1/2 inch in any direction. Too much stuff in the way. If I could've gotten my hand in between the engine and the harness I could've cut that extra hour off the job. The Bosch sensor has a bigger outer casing, and the hardest part of the job was getting the O2 socket off the new sensor after tightening it up.
 

CSVT_2004

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Messages
2,406
Location
Wisconsin
this info saved me a big headache and time concering those codes

8)Clear Codes/Reset PCM by removing Fuses 4 and 11 for 10 minutes.
Some CEL codes that may give you the impression that this particular sensor needs to be replaced:
P0133-â​
oeHeated upstream 02 sensor circuit slow response (bank 1)â
P0171-â
oeâ •System too Leanâ • (bank 1)
P0172-â
•System to Richâ • (bank 1)
P1131-â
oeLack of upstream heated oxygen sensor switch-Sensor indicates Lean (bank 1)â
P1132-â
oeLack of upstream heated oxygen sensor switch- Sensor indicates Rich (bank 1)â
**Would like to thank â
oeWilliamâ • and â oeannakobyâ • for past threads that made some of this information
possible, written by â
oemycainsbrokenâ •**

**Pictures and Updates by Crystian C. (Golden Tour) 8/11/05**

What about P0420? Is that a possible code for this sensor needing replacement?
 

mikeal21

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Sep 20, 2007
Messages
10
Its a tough job, glad its done

Its a tough job, glad its done

I got a sensor socket at Northern Tool for $4. Worked great on o2 by oil filter. But the back one was a beast. Tried sensor socket with straight ratchet, stubby, all kinds of flex extensions. None of them worked , almost had it with a breaker bar, but it keep slipping.
Got with a 22mm box end, modified/cut open to slip threw wire onto o2. It was part of a set $7 that I bought for a 15mm/ oil plug. I didn't have. Knew an extra 22mm would come in handy then.
If I designed a (perfect) wrench/mod for this it would be 8in. or less. Offset, makes it easier to get grip on o2. I cut box end open 1/4in. that worked well, but offset would be better I think. They make a offset o2 socket, that might work well also. I think someone else spoke of that in another post, I saw it also at Northern Tool. Wasn't sure if it would work when I saw it, didn't hit me at the time. But with a stubby ratchet would maybe work well??? The socket wrench type was too bulky.
You have to go left handed, from the passenger side/left under wire harness. Use a crow bar to hold up harness slightly to get in there and see what your doing. I have a nice bruise to show for that one but, I'm not gonna do that again anytime soon.
It took me and help an hour??? Trying wrong ways to do it. Its not fun but considering I paid $85 on Ebay for all 4 sensors and there all up and running great. I did OK. Knock on wood...
 

projectSHO89

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Sep 19, 2002
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St. Louis, MO
What about P0420? Is that a possible code for this sensor needing replacement?


Not very likely. See all the P0420/P0430 discussions in the regular troubleshooting forum.

However, a faulty upstream sensor, left unattended, will cause excess fuel to be dumped into the precat and will ruin it, causing a P0420/P0430 after the upstream sensor is replaced.

Steve
 
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