CEL, CODE 67, Catalyst Efficiency

[dallas23]

I have a 98 honda civic, i put in a Magnaflow Cat back system with a high flow race cat, and ever since it has tripped my CEL on with code 67. Code 67 is "Catalyst system efficiency below threshold", my question is, does any one know if the is a way to bypass this sensor so my ecu will n o longer detect this fault??, if not i am going to have to put my stock cat back in. Thanks

[littledan]

i have a 97 prelude vtec. i also replaced the stock catalytic converter with a resonated test pipe. the reason your ecu is tripping the code, is due to your secondary o2 sensor. the primary o2 sensor takes the initial reading. then the gases pass through the cat and get read by the secondary sensor. if the gases are not "cleaner" at the secondary o2, the ecu knows somethign is not workign correclty and trhows the code.

there are 2 ways around this.

you could by an o2 simulator and wire it into your secondary o2 harness. this will simulate a secondary o2 with a properly working cat.

or you can do it my way. what i did is just plug the secondary o2 hole. i left the secondary o2 sensor connected to the elect harness and simply zip tied it tucked away in the engine bay. this way the 2nd o2 reading is "cleaner" than the primary and the ecu is happy.

hope this helped.

[rc2002]

Are there still O2 sensors before and after the cat? Your civic has a cat right after the exhaust manifold. So you'll need to extend your second O2 sensor behind the cat to get a proper reading. This can be done by welding a bung into the piping directly after the cat.

Typically a high flow cat and catback exhaust won't cause a check engine light. If you have wired the second O2 sensor properly, there may be something else that you need to trouble shoot - the O2 sensors may need to be changed.

[dallas23]

Originally posted by littledan
i have a 97 prelude vtec. i also replaced the stock catalytic converter with a resonated test pipe. the reason your ecu is tripping the code, is due to your secondary o2 sensor. the primary o2 sensor takes the initial reading. then the gases pass through the cat and get read by the secondary sensor. if the gases are not "cleaner" at the secondary o2, the ecu knows somethign is not workign correclty and trhows the code.

there are 2 ways around this.

you could by an o2 simulator and wire it into your secondary o2 harness. this will simulate a secondary o2 with a properly working cat.

or you can do it my way. what i did is just plug the secondary o2 hole. i left the secondary o2 sensor connected to the elect harness and simply zip tied it tucked away in the engine bay. this way the 2nd o2 reading is "cleaner" than the primary and the ecu is happy.

hope this helped.

Thanks, that sounds like a good idea and as long as the CEL stays off it will be good, cause i fucking hate lights on my dash, thanks Buddy.