Cat bypass and oxygen sensor question
07-23-2009, 01:06 PM
#1
Rennlist Member
Thread Starter
Cat bypass and oxygen sensor question
I've had cat bypasses on my '96 993 for a couple of years now and like them. But now I've got an O2-sensor CEL that won't go away. For the two downstream O2 sensors, I pulled them inside the engine bay and zip tied them out of the way. About a year ago one of them threw a code and the CEL light came on. I cleared it and it stayed off for many months. But it came back recently and won't stay off even after clearing it.
So, I have three questions:
1. Do the O2 sensors have the same service life when they're screwed into the exhaust versus when they're hanging free?
2. Is there any way to test them to make sure they're faulty? (This is the first 911 I've owned that used O2 sensors...)
3. Can the faulty O2 sensor be simply removed, or jumpered, being that I don't need it (or its partner) to be functional? Any reason I have to buy a brand new O2 sensor just to fool the computer into not turning the CEL on?
So, I have three questions:
1. Do the O2 sensors have the same service life when they're screwed into the exhaust versus when they're hanging free?
2. Is there any way to test them to make sure they're faulty? (This is the first 911 I've owned that used O2 sensors...)
3. Can the faulty O2 sensor be simply removed, or jumpered, being that I don't need it (or its partner) to be functional? Any reason I have to buy a brand new O2 sensor just to fool the computer into not turning the CEL on?
07-23-2009, 03:06 PM
#3
Rennlist Member
Have you tried using an o2 sensor spacer? Audi/vw guys use them when they install cat bypass pipes. You can google it and a bunch of hits show up...
http://www.maperformance.com/ams-o2-...lio2space.html
http://www.meganracingperformance.co...n-p-66535.html
http://forums.vwvortex.com/zerothread?id=3705618
Caveat: I have no personal experience with them.
http://www.maperformance.com/ams-o2-...lio2space.html
http://www.meganracingperformance.co...n-p-66535.html
http://forums.vwvortex.com/zerothread?id=3705618
Caveat: I have no personal experience with them.
07-23-2009, 05:02 PM
#4
Rennlist Member
Thread Starter
Gerry -- unfortunately I'm overseas right now, or else I'd be able to go to the garage and read the code. Now that I'm looking at a code chart, I can see that this post is probably premature, and I should wait till I get home to see precisely what code I'm looking at. I know it's one of the post-cat sensors, I just don't remember what exact fault the code identified.
Eric, thanks for the links -- although I'll probably just stay with the zip-tie method, because otherwise I'd have to weld those O2 bungs into the cat bypasses...probably not worth it.
Eric, thanks for the links -- although I'll probably just stay with the zip-tie method, because otherwise I'd have to weld those O2 bungs into the cat bypasses...probably not worth it.
07-23-2009, 05:57 PM
#5
Rennlist Member
Here's another:
http://www.gocpt.com/products/4/CPTO...nsorSpacer.php
07-23-2009, 06:00 PM
#6
Rennlist Member
p.s. is your O2 sensor exposed to water? Water is bad for them, that's why custom installers must be careful about how they're located; if exhaust condensation collects on the tip because it's pointed up, it'll kill it. So I imagine water spray would do the same.
07-23-2009, 07:02 PM
#7
Why would you weld them, space issues? It's just a plug-n-play screw-in.
Here's another:
http://www.gocpt.com/products/4/CPTO...nsorSpacer.php
Here's another:
http://www.gocpt.com/products/4/CPTO...nsorSpacer.php
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07-23-2009, 07:53 PM
#8
Rennlist Member
I think what he is saying is that there are no provisions to screw in the 2 post cat O2 sensors on an OBDII cat bypass. There are only provisions to screw in the 2 pre cat sensors. The post cat sensors need to be tied off somewhere. At least this id the deal with my Dach X pipe.
07-24-2009, 02:49 AM
#11
Rennlist Member
Thread Starter
Haha, ok I won't!
I'd like to figure out some way of removing them entirely, as they're a sensitive and expensive item that is exposed, as Eric noted, to water and contaminants, which surely shorten their lifespan. I might try the O2 sensor simulators.
I'd like to figure out some way of removing them entirely, as they're a sensitive and expensive item that is exposed, as Eric noted, to water and contaminants, which surely shorten their lifespan. I might try the O2 sensor simulators.
07-24-2009, 08:25 AM
#12
Race Car
The correct way to take them out of the system is to have the ECU reflashed with them taken out of the program. Steve W would be better versed on this than me, I would check with him.
07-24-2009, 08:40 AM
#13
Rennlist Member
Thread Starter
I've got a '96, which as I understand it can't be reflashed. Plus, there's a decent likelihood that in the coming couple of years I'll have to move to a state that has emissions testing, in which case I'll have to put the cat back on.
So I think that maybe for now the best bet would be to get those O2 sensor simulator doohickeys. Not sure exactly how they work, but I'll do some googling and post what I find...
So I think that maybe for now the best bet would be to get those O2 sensor simulator doohickeys. Not sure exactly how they work, but I'll do some googling and post what I find...
07-24-2009, 08:49 AM
#14
Race Car
I've not heard of anyone using those with our car that worked. If its just the CEL issue, and there's no inspection holding you up, just let it go. Leave the O2's in the loop and tied up out of the way. If you have to put the cats back on...........problem solved. I should have seen you had a 96.........its early 
07-24-2009, 08:52 AM
#15
Rennlist Member
Thread Starter
That's basically what I've done for the past 8-10 months, and I'm just getting tired of looking at the orange light on the dash...and having people riding with me say, "hey, your check engine light is on!" Plus, if the CEL is always on, isn't it true that I won't be able to tell if the car throws an important code?