DIY: Post-Cat O2 Sensors + Pre-Cat O2 Sensors

at what milage should the post-cat be changed?? I change my pre-cat at 50k...great diy by the why

Same things for Post O2's 100k

And Thanks

I just replaced my rears yesterday. This guide was helpful but I would like to add 1 thing.

When pulling out the old rear ones, I tied a string to the end on the top side, so when I needed to route the new sensors wire back to the top, I just tied it to the string and pulled.

excellent diy write up. what a PIA though! btw, i found the post cat o2 (lambda) sensors on realoem.com but cant find the pre-cat senors, ne1 have the part numbers for those?
Post cat:

just found the write up for the pre-cats, thought i would cross-link: http://forum.e46fanatics.com/showthr...=o2+sensor+diy

nice DIY
I need to do this soon

If I disconnect my pre-cat 02 sensors will this allow me to assess whether my power problems are due to a bad Cat? i.e. if my power problems are solved its the bad reading from the o2 sensors causing a poor air/fuel mix. Will disconnecting the pre-cat 02 sensors allow this?

bumpin to remind myself to change these
I think i'll do the precats first then post when im not as lazy

Great write up

Great write up, very useful but one thing missing.

Error codes refer to bank 1 or bank 2. As I understand it, bank 1 is cylinders 1-3, bank 2 is cylinders 4-6.

Although when you get into the job you can probably work it out (am I right assuming cyl 1 is at the front and cyl 6 at the back ?), it would be really useful if the sensors and connectors in the pictures had been labelled as to which was the bank 1 or bank 2 post-cat sensor and plug. If I get a bank 1 error (P0420 - cat bank 1 below efficiency actually, but the car's passed an emission test in the MOT so I suspect post-cat sensor at fault, not cat) I'd like to know which sensor to look at (so I know in advance whether it's the "easy" one or the "hard" one I'm looking at changing).

Can anyone help with that info ?

Vexed !!!

Cheapest price I can find for OEM (post-cat sensors) Bosch part number 0258005109 in UK is: Bosch Direct Fit - (wires 4, cable length 990mm) £71.68 inc VAT & UK deliv. (= $139.55 USD !!!)

That's $80 more, for the same OEM Bosch part that I've seen advertised in the US for $58-$60 !!!

http://www.lambdasensor.com/main/bos...tem=0258005109

http://www.rockauto.com/catalog/rafr...1433864k279826

http://www.autohausaz.com/search/pro...xygen%20Sensor

Can anyone recommend a supplier who will supply at similar prices and ship to UK at a reasonable price ? I'm gonna have to check around the web further too I think.

I got mine from KO Performance. 55 bucks each!

guys, my car is giving faults:

-AfterCat oxygen sensor short to B+, Cyl #4-6
Peake Research code: 15 9F...I keep getting this code

-AfterCat oxygen sensor disconnection, Cyl #4-6
Peake Research code: 15 D8...I only had this code once



So I am only going to replace the one post-cat O2 sensor, not both.
Is that OK? Or is there some reason I am unaware of that I should do both?

Also Im not sure which sensor is for cyl #1-3 and cyl #4-6. Does anyone know?

Any other advice is appreciated
Thanks for the help!!!!

Originally Posted by Cheezemurda

I got mine from KO Performance. 55 bucks each!

Realoem gives me a part number 11781433940, which is $151 from KO.
Even if they'd ship internationally there's no savings to be had for me there.

Originally Posted by markovnikov5

guys, my car is giving faults:

-AfterCat oxygen sensor short to B+, Cyl #4-6
Peake Research code: 15 9F...I keep getting this code

-AfterCat oxygen sensor disconnection, Cyl #4-6
Peake Research code: 15 D8...I only had this code once



So I am only going to replace the one post-cat O2 sensor, not both.
Is that OK? Or is there some reason I am unaware of that I should do both?

Also Im not sure which sensor is for cyl #1-3 and cyl #4-6. Does anyone know?

Any other advice is appreciated
Thanks for the help!!!!

Anyone?
Which POST CAT sensor is for cyl #4-6??

Superb write up, excellent thread. I thought I'd add a how-to for the other part of the job, if you're changing your sensors you've probably got a fault light which needs clearing. Here's how:
http://forum.e46fanatics.com/showthread.php?t=576850

Originally Posted by tony325ci_51

Error codes refer to bank 1 or bank 2. As I understand it, bank 1 is cylinders 1-3, bank 2 is cylinders 4-6.

Although when you get into the job you can probably work it out (am I right assuming cyl 1 is at the front and cyl 6 at the back ?), it would be really useful if the sensors and connectors in the pictures had been labelled as to which was the bank 1 or bank 2 post-cat sensor and plug. If I get a bank 1 error (P0420 - cat bank 1 below efficiency actually, but the car's passed an emission test in the MOT so I suspect post-cat sensor at fault, not cat) I'd like to know which sensor to look at (so I know in advance whether it's the "easy" one or the "hard" one I'm looking at changing).

Can anyone help with that info ?

Originally Posted by markovnikov5

Anyone?
Which POST CAT sensor is for cyl #4-6??

Summer must be here, we had a warm day on Sunday so I got outside under the car and did an oil change.
While I was under there I thought I'd trace the exhaust pipes, finally take some pics and answer this question.

Both post-cat sensors are easy to reach but the Bank 2 sensor (cyl 4-6) will be more fiddly to undo, as the 22mm "sensor socket" (with a slot in it, picture attached) will have to be turned and repositioned just like with a normal spanner. Due to the wires you can't just undo it with a rachet. An open-ended 22mm spanner will be fine for Bank 1 (cyl 1-3) sensor (You couldn't use a "sensor socket" on this, there isn't enough clearance to get a rachet on it.).

(You won't have the advantage of being able to see the view in the 2nd picture. This was taken by holding a small camera in the gap up above the exhaust).

Photos include details of post-cat sensors, and the tools required to replace each:

For anyone wanting to download or print this DIY, I made a nice setup for a friend, and figured someone might be interested in this.

Screen shot :


DIY (PDF)
http://www.mediafire.com/?wbehdbbf3px

For reference:

wow thanks tony, thats great information, just what I needed. thanks to sdbimmer also

Originally Posted by tony325ci_51

Great write up, very useful but one thing missing.

Error codes refer to bank 1 or bank 2. As I understand it, bank 1 is cylinders 1-3, bank 2 is cylinders 4-6.

Although when you get into the job you can probably work it out (am I right assuming cyl 1 is at the front and cyl 6 at the back ?), it would be really useful if the sensors and connectors in the pictures had been labelled as to which was the bank 1 or bank 2 post-cat sensor and plug. If I get a bank 1 error (P0420 - cat bank 1 below efficiency actually, but the car's passed an emission test in the MOT so I suspect post-cat sensor at fault, not cat) I'd like to know which sensor to look at (so I know in advance whether it's the "easy" one or the "hard" one I'm looking at changing).

Can anyone help with that info ?

Hey Tony, I have the exact same error on my 03 M3 saying htat efficiency for bank 1 is below threshold. Did you fix your problem and did the light go off? I was just wondering if you could help me out because I'd like to do it myself. Was it a post-cat sensor and did you just have to replace one? Any help would be appreciated. Thanks.