ok so over the weekend i installed a high flow cat in my car its a 5th gen prelude SH.. I take it to the shop and the guy welds everything up. As soon as i get in the car I start her up and there ya go I get a frickin cel my Check engine light and my atts light comes on. I immediately think damn i fucked up my secondary o2 sensor. So my question to u guys is how do i go about installing a secondary o2 without one going bad on me. also is this a common problem when putting in a high flow cat. I know I heard about o2 sensors burning out and stuff like that so is that my problem. AM i suppose to buy an aftermarket o2 sensor because of the increase airflow and what not. Would replacing the o2 sensor just f*uk up the new one also. I don't have big money to waste on this thing. Somebody please let me know what to do. sorry for my lack of experience post but i really need answers. High flow cat guys please chime in on this one.

 

i knew a guy with a 5th gen base model who had a random tech high flow cat. he said he had a CEL since the day he put it on, and could never get it to go away, even after changing the o2 sensor twice. i think your only option would be to buy/make an o2 sensor simulator.

 

damn that sucks *****. So the o2 sensor always goes bad when u put on a high flow cat? IS this a typical problem?

 

well, you can just drive your 5th gen with the CEL on, but it will get shitty mpg is all, but with the aftermarket exhaust and high flow cat, that may not be the issue. the only method I have found to be effective is to put in an OBD1 ECU, preferrably a P72 from a GSR. some u can buy with chips (JUN, SKUNK2, HONDATA) and just get the OBD2- OBD1 conversion harness and plug it in. some people have also located the actual wire/pin connection on the ecu that controls the ecu memory after you shut the car off and spliced in a switch so every time you shut the car off it automatically resets. i wouldn't recommend this, but it's been done. you may try contacting Hondata for more info bro.

 

well i understand what u mean i want to switch out the ecu for a obd 1 but I still have the factory warranty and i have to keep it that way. I can't really rish them droppin me from coverage. Is there a aftermarket o2 sensor or something that i can get that won't throw cels. Is there a o2 sensor that is meant for hi flow cats. I mean why would they give u the o2 bung if ur o2 sensors are gonna get messed up?

 

[\<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98ludepimp &raquo;</TD></TR><TR><TD CLASS="quote">well, you can just drive your 5th gen with the CEL on, but it will get shitty mpg is all, but with the aftermarket exhaust and high flow cat, that may not be the issue. bro. </TD></TR></TABLE>

Not always true. Like i just mentioned in another thread - there are two o2 sensors on obdII cars. The first o2 sensor - close to the manifold is for fuel(lean/rich...**** like that). The second o2 sensor - at or after the cat is for the catalytic converter efficiency. So, you could just be tripping a code - saying that the catalytic converter isn't efficient. You'll have to actually pull the code to let us know what it is.

If its secondary - thats just the o2 sensor that controls the efficiency. And as long as u have the high flow cat on, the MIL will be on. Only way to combat that is to get another cat.

 

so you are saying that in order for me to get rid of the code i should buy another hi flow cat because the one that i am using is basically garbage because its no longer effiecient

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Fastkill &raquo;</TD></TR><TR><TD CLASS="quote">so you are saying that in order for me to get rid of the code i should buy another hi flow cat because the one that i am using is basically garbage because its no longer effiecient </TD></TR></TABLE>

No longer efficient, as in effectively catalyzing the gases.

From a motor standpoint, your cat is more efficient. From an EPA standpoint, it sucks *****. That is what they are saying.

To be sure though, you need to pull the code. What kind of cat did you put in?

.....and, it is an actual high-flow cat and not a test pipe?

 

well it is a Carsound / magnaflow cat direct bolt on. I had to shorten the pipe after the cat about 3 inches so that it would fit in place. also yes i am sure about it being a hi flow cat. I am gonna pull the code tonight so i will let yall know the official cel

 

yea like Lewdin' Incognito said let us know what kind of "high flow cat" you got because if its the one from eBay you will have problems with that. i got my car and it had one of those on it after about a month i got a cel and that was the reason. i got a random tech cat changed the o2 because the old one was bad and thats it

 

I had to shorten the pipe after the cat about 3 inches so that it would fit in place.???? if it is a direct bolt on you shouldnt have to shorten anything

 

i had the same problem on my 5th gen, i had a custom 2.5'' exhaust done with the 2.5'' header collector mod and i used a high flow magnaflo cat and resinator it was working great for about 4 months then one day the cell came on for catalyst efficiency below threshold so i put a o2 sim and never had the problem again

 

well like u guys said i took the car to the local autozone to have the codes pulled.. It threw code P0141 or 65 based on the flashing CEL.. It meas 02 sensor heater circuit malfunction (Bank1 Sensor 2). So now what is the plan.. does this mean that i need to buy a new o2 sensor?

 

Just install a plug into the o2 bung and mount the o2 sensor onto the heat shield. This way, the o2 sensor thinks that it is running super efficient because there are no emissions detected. It worked for my buddies ITR. Give that a shot.

 

I've had my Carsound 2.5" cat for about 7 months now and I've never thrown any CEL codes at all.