Cat bypass CEL question
#1
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I recently installed a cat bypass pipe in my 96 993 C2. First I installed all four O2 sensors in the bypass pipe. Not surprising but after an hour long drive the CEL came on. Codes suggested a Cat problem. So I cleared the faults and removed the rear O2 sensor and "hung" it up inside the engine compartment so that it could breath some clean air.
No problem until I did a long drive down to California. After four hours of continuous driving I got a CEL again.
Where are you mounting the rear O2 sensors or what are you doing to overcome the CEL issue for Cat bypass pipes?
Thanks
Ron
No problem until I did a long drive down to California. After four hours of continuous driving I got a CEL again.
Where are you mounting the rear O2 sensors or what are you doing to overcome the CEL issue for Cat bypass pipes?
Thanks
Ron
#3
Race Car
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This has been discussed before, but you need to ground them (keeping the O2's connected to the wire loop and sniffing) You got a bad cat reading because the system found no difference between the pre and post O2's. What you have created is a VERY lean mixture situation. Hopefully no damage has been done to the motor, in addition, it will take a little time to react to the new (grounded and sniffing) readings.
#4
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Originally Posted by 993inNC
This has been discussed before, but you need to ground them (keeping the O2's connected to the wire loop and sniffing) You got a bad cat reading because the system found no difference between the pre and post O2's. What you have created is a VERY lean mixture situation. Hopefully no damage has been done to the motor, in addition, it will take a little time to react to the new (grounded and sniffing) readings.
.....is dangerous to the motor ? the next week i install a fabspeed catalytic converter bypass pipes ! i have only one oxygen sensor after and before.
#5
Rennlist Member
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I kept the sensors connected and mounted on sturdy brakets 1/8" from the by-pass pipes and had no CEL problems for 1.5 years. I finaly did get a CEL and got the bad cat codes. Water/time/road dirt started wearing on the sensors and they eventually started to provide differing and "bad" O2 readings which eventually tripped the CEL. I ussually end up having to clean the sensors regularly and have avoided the CEL. But, no matter what I have done, I have always end up with a running lean issue. The smell tells me it is time to clean the sensors. I will end up putting the CAT back due to my pending NJ Emmisions test and the concern about engine damage due to engine damage.
Tom
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96 993 Cabrio - Black
21K miles
Fabspeed exhaust
Carbon fiber air box
Strut bar
Rennsport pedals
18" Turbo twists
One lead foot
Tom
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96 993 Cabrio - Black
21K miles
Fabspeed exhaust
Carbon fiber air box
Strut bar
Rennsport pedals
18" Turbo twists
One lead foot
#6
Race Car
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Originally Posted by maximo993
.....is dangerous to the motor ? the next week i install a fabspeed catalytic converter bypass pipes ! i have only one oxygen sensor after and before.
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The installation of a cat bypass isn't the problem, its the way it was installed that is.
#7
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OK. just to be clear. My last install was for the pre-cat O2 sensors to be installed in the bypass pipe. This registers a pre cat sniff. The post-cat O2 sensors are still wired into the system and were left suspended in the engine compartment to sniff clean air. After four hours of continuous driving I got the CEL light.
Where did I go wrong? Still connected to the wiring harness is grounding them.
Thanks
Ron
Where did I go wrong? Still connected to the wiring harness is grounding them.
Thanks
Ron
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#8
Race Car
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Ron,
You should clamp them to ground. The wire harness to O2 doesn't count if the O2 isn't grounded. I have sold quite a few bypass pipes in the last year and a half and to this point, no one has complained about a CEL after following that one direction. Try it and see what happens.
You should clamp them to ground. The wire harness to O2 doesn't count if the O2 isn't grounded. I have sold quite a few bypass pipes in the last year and a half and to this point, no one has complained about a CEL after following that one direction. Try it and see what happens.
#9
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I thought the post-cat sensors were only there as part of OBD II to police the functionality of the cat to ensure it was cleaning up the exhaust and that the post-cat sensors have no effect on the mixture?
#10
Three Wheelin'
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My Son used O2 sensor spacers (buy em at auto parts store) on the post sensors (had to drill them out) to move the sensors out of the exhaust gas path. This seems to work fine. Not sure if there is enough room in the P-car. This might be a solution...
Good Luck!!!!
Good Luck!!!!
#11
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Thanks to everybody for their input. I will try to "ground" the post-cat O2 sensor. You are correct. They are connected and not addtionally grounded. So, after they are grounded I should 1) get no CEL and 2) the mixture (not too lean) will now be improved?
I did a 2400 mile drive with the CEL on.
Thanks again.
I will let you all know how it works out.
Did I mention it is LOUD without the cats.
Ron
I did a 2400 mile drive with the CEL on.
Thanks again.
I will let you all know how it works out.
Did I mention it is LOUD without the cats.
Ron
#12
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Just got the CEL code retrieved. It is P0136
Went on line and it says this code is "P0136 Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2)"
So for all 2500 miles I drove down to California and back I got one fault and that was after 4 hours of steady driving.
So if I have to ground them why did I not get a fault for the other side?
Thanks
Ron
Went on line and it says this code is "P0136 Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2)"
So for all 2500 miles I drove down to California and back I got one fault and that was after 4 hours of steady driving.
So if I have to ground them why did I not get a fault for the other side?
Thanks
Ron