O2 sensor removal from cat..Help!

[BikeOps]

In anticipation of the new exhaust, I decided to yank the old one today. pulled the pipes from the head as well. Can't say enough about PB blaster! Made breaking loose the nuts and bolts ultra easy. Here's the problem..the O2 sensor is loose but the connected wires turn with it. Don't want to stress the wires. A previous post said that the tank could be propped up instead of being removed altogether in order to disconnect the sensor at the opposite end underneath the tank. Is there a cannon plug connection that I should be looking for? Visibility is not so clear without the tank completely off. Help please.

[twodear]

Yes, there is a two wire plug way up under the fuel tank to the harness that runs to the ignition module; you'll need to drain the fuel and remove the tank to find it. If I recall correctly there is a red and a brown wires (maybe it was a brown with a red stripe, or my memory could be completly incorrect, etc etc) and the harness is about 2ft long. The best way to trace the wires is to pull and push the wires slightly while looking for movement up top, you should be able to locate the correct pair fairly quickly.

[Anton]

It's a pain in your ass, but you can always hold the plug and spin the pipe.

[BikeOps]

Thanks, I was trying to keep from removing the tank if it was possible. But I gotta do what I gotta do.

[BikeOps]

Holding the plug and spinning the pipe...that sounds interesting but in my case it would be holding the plug and spinning the "easy bake oven" (CAT). Is this possible? PITA or no, is this even possible? Tell me more.

[felixbobcat]

I just replaced my pipes and did not have to remove the tank and unplug the sensor. It's only screwed in by about three turns so there's enough slack to unscrew it without unplugging it. Just be very carefull and hold on to the plastic housing protecting the wire and make sure they don't get too twisted at the sensor. When you put it back in, retwist the sensor counterclockwise the same amount of turns it took to come out, again just be careful. It will save you a hell of a lot of time and agrevation.

[JonyRR]

ahhh...but then you don't get the experience of seeing what is under the tank..and if you're like me, vomiting at all the excess wire runs and dead-end harness connectors for something else..
and then taking a deep breath and performing a harnessectomy to exorcise all that dead, useless wire and as a bonus, understainding where the 02 sensor plugs in at and getting to that connector.
BMW is different...small gauge wire but way too much of it.
I'll bet I yarded half the harness out onto the bench with no ill effects and now I understand the entire wiring schema of my scoot. I coundn't BELIEVE all the extra crap in the harness...BMW must use only one harness for the entire oilhead configuration series...

[BikeOps]

Thanks everybody....BUT ! felixbobcat... you Da Man. Followed your advice...one sensor out. No strainin' and no drainin'. Let it be known for others unclamp the wire from the side of the motor about two clamps upstream from the sensor. With each turn of the the sensor feed these twists religiously up the wire evenly...five turns of the sensor..Done! ( To be fair the manual directs to remove the tank for this job ).

[JonyRR]

HEY...THAT'S CHEATING!!!!!!!!!!!
SOMEONE CALL THE OEM PROCEDURE COPS (OH, DOCTOR, DOCTOR.....)

[BikeOps]

LOL ! LOL !

[Ole Bike]

Originally posted by BikeOps
Thanks everybody....BUT ! felixbobcat... you Da Man. Followed your advice...one sensor out. No strainin' and no drainin'. Let it be known for others unclamp the wire from the side of the motor about two clamps upstream from the sensor. With each turn of the the sensor feed these twists religiously up the wire evenly...five turns of the sensor..Done! ( To be fair the manual directs to remove the tank for this job ).

The wires are pretty strong and the outer sheathe flexible. Good to unhook the cable from the clip alongside the cylinder for extra play to work with. Special pricey O2 sensor wrenches are available but not essential on the S.

Good to replace copper gaskets such as the one on the O2 sensor. Anybody know where to find spare copper gaskets - not available through BMW? Heating cherry red on the kitchen stove will anneal the copper nicely.

Quite a mystery about what chemicals can and can't be used on (or even upstream) from an O2 sensor because the thing can get fouled and destroyed. I think anti-seizes are OK but some silicon products aren't. If in doubt....

[Rapid Dog]

...um, JonyRR, what happens if you just leave the cat plug out completely and plug up the bung?...

[JonyRR]

'um, JonyRR, what happens if you just leave the cat plug out completely and plug up the bung?...'
you know what happens. it runs mucho better and you can run some NITRO!!!!! in the tank...hehehehe.
I recommend Klotz or Price Fuels Max Race

[Rapid Dog]

serious? cuz I've gpt the Techluison box and I'm thinking of removing it due to massive fuel consumption issues...I think it's tied in there somehow...

[JonyRR]

the cat code plug runs a particular OEM map for the plug type and scoot type. if you yank the polug, it defaults to a semi 'limphome' or rich mode and disregards the 02 sensor input.
if your techlusion scoot is running rich, try leaning out the techlusion...but one disadvantage of the tech is that it can only RICHEN the mixture over baseline, it can't lean it out. if it's running rich, try setting the tech to a point where it's not adding any fuel.
if there's an 02 sensor in the system, the 02 sensor could be hosed, which, again, would default the moronic to a 'limphome' mode...usually.
02 sensors are considered wear items; I just put 2 (yes, my bmw cage needs 2) in my car as they were gone after 100K+ miles.
how do you tell if your 02 sensor is toast? massive running rich or lean with no other explanation, over 50K miles or 5 years, or pull it and see if the little holes in the tip are plugged with carbon. a generic one (NOT a bmw part# but napa has 'em, moybin knows the part#) is like $50.00 or so...

[Peter Parts]

Originally posted by Rapid Dog
serious? cuz I've gpt the Techluison box and I'm thinking of removing it due to massive fuel consumption issues...I think it's tied in there somehow...

Which Techlusion, the one that uses the O2 sensor or the one that unplugs it?

What consumption is seen by the PCIII users - gone up or stayed the same?

[Rapid Dog]

well, if I remember right, the Techlusion 1031 uses al the BMW connecors, simple plug and play. Part of the install requires unplugging the O2 sensor altogether, and maybe replacing it with part of the 1031 harness. I'll have to chuck the 'structions.

I guess what I wanna know is if I disconnect the 1031 and take it out of the loop, can I also leave the 02 sensor unplugged...

[Rapid Dog]

...all I know is with spirited riding last Saturday, my reserve light came on at 115 miles!!! That's like going from appx 40mpg to a little over 30mpg!

[JonyRR]

.spirited riding'.....gasp!...you .....didn't.....break...the SPEED LIMIT, did you. You nasty boy. shame.
unplugging the 02 sensor will also result in the default full-rich mode; like pulling the CCP.
I can see how flogging the snot out of a good-running RT would drop the mileage a bit, but isn't 40 a bit on the low side already? It sounds like you are running somewhat rich, indeed.
black soot inside the pipe? black plugs? fuel-ey smell? under very rich conditions, high engine temps?
that's one reason I waited for the bmw-specific PCIII and didn't pop for a techlusion.
how's the air filter?

[Peter Parts]

Originally posted by Rapid Dog

I guess what I wanna know is if I disconnect the 1031 and take it out of the loop, can I also leave the 02 sensor unplugged...

The ECU pays little attention to the O2 sensor and with it disconnected, even less. Ignore that comment if you love superslabs.