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I have a 2003 Civic HX with 3 thats right 3 02 sensors, now i put on a hp racing header an high flow cat W/ a skunk 2 racing catback, an boom check engine light!!! now i got 2 02 senor bypasses on with the check engine light still on, i don't have one on the first don't worry, i'm just wondering if there are any other civics out there my year or so that have had the same problems an how did you fix them. An what models have 3 02 sensors lx/dx/hx????????????? i take the ex's only have the 2????????

And maybe does anybody know what a auxillery emissions control malfunction is i checked it once but can't remember if that was the exact read out......

 
Rep Power: 812

not sure what to do in your case, but there are two cats on that car.

 
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yeah, i have to o2 bypasses on there an either one of them isen't working properly or i got another problem i guess??

Just looknig for some idears

 
Rep Power: 286

put a second O2 sim on the 3rd o2 sensor.

It has to notice 2 decreases in fuel. First O2 sets the base. 2nd O2 senses how well the 1st cat is working. 3rd O2 senses how well the 2nd cat is working. So if the #2 and #3 sensors sense the same thing, then it will think that the 2nd cat is bad. So simply put a second sim on the 3rd O2

 
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there are 3 o2 sensors total on my car,ok now i have 2 o2sensor bypasses on, one on the second toward the back of my exhaust an then i have another on the 3rd after the cat would be. so your saying to put another o2 ensor bypasses on my car in the first spot???

 
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no, a second sim. on the last o2 sensor to indicate a lower level of "smog" compared to the first cat.

first o2 sensor>second>third <--- add a second o2 sim. to this sensor

 
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i got to 02 bypasses on the last 2 but i ordered a o2 sim an it should be here tuesday.