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Discussion Starter · #1 ·
Hey guys,

I installed my CPE turboback with a high flow cat maybe 3 weeks ago. The system sounds and feels great. However, in the last couple of days my CEL is constantly coming on. I disconnected the battery to reset it, but it always comes back after 100 or so miles or driving. I thought the straight pipe could cause the CEL but the high flow cat shouldn't. Does anybody have a similar problem? If so, what is the fix?

Thanks,

Brian
 

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You should have the code scanned and see what it is. Even having a high flow cat does not gaurantee no CEL, because it still may flow too much and the sensors might not like it.
 

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The CP-E downpipe with the high-flow cat is known to cause a CEL, which is produced by the following code:

P0420 Error Code: Catalyst System Efficiency Below Threshold (Bank 1)

Basically, there is too much exhaust flowing through the cat. The second O2 sensor is expecting to see more of a change in the exhaust reading from the O2 sensor before the cat. Bottom line, there's nothing wrong with your car IF this is the only code you have, and using an O2 space WILL NOT correct the problem, as it has been tried before by other forum members (including me). You should also not be experiencing any reduction in engine performance as a result of this code. Hope this helps.
 

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FUNCTION OVER FORM
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The CP-E downpipe with the high-flow cat is known to cause a CEL, which is produced by the following code:

P0420 Error Code: Catalyst System Efficiency Below Threshold (Bank 1)

Basically, there is too much exhaust flowing through the cat. The second O2 sensor is expecting to see more of a change in the exhaust reading from the O2 sensor before the cat. Bottom line, there's nothing wrong with your car IF this is the only code you have, and using an O2 space WILL NOT correct the problem, as it has been tried before by other forum members (including me). You should also not be experienceing any reduction in engine performance as a result of this code. Hope this helps.
So what's the purpose of buying the CP-e DP with cat if it doesn't keep the CEL from coming on? That's why I purchased it, otherwise I would of went with the non-catted version. :(
 

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So what's the purpose of buying the CP-e DP with cat if it doesn't keep the CEL from coming on? That's why I purchased it, otherwise I would of went with the non-catted version. :(
You got me there bro!

I actually used to have the non-catted version on my car, but I got tired of headaches from the exhaust smell, and I also want to be able to pass emissions when I get my car inspected in the future. The difference in terms of performance is more whp gains through mid-range and top-end with the non-catted version (at the expense of low-end wtq), versus smaller mid-range and top-end gains and no low end torque loss with the catted version. I was not expecting to have a constant CEL for the DTC referenced in my previous post, but I can always clear it with a scanner if it bothers me enough. If not for the emissions thing, I would have probably stuck with the non-catted version. I may even buy another one for the track days in the summer...

Of course, these are just what I experienced myself. Others may get different results based on other mods installed, etc. The thing that sucks about this though is that CP-E advertised the non-catted version as having a build in CEL eliminator. No such device was included on mine, and I don't know of anyone else that has one either. Some people will probably agree that the performance gains from the part mitigate this "oversight" on CP-E's part. You be the judge....
 

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Discussion Starter · #6 ·
Thanks for the quick responses, cjd, prime and Tufast.

Yes, I will have to say that the primary reason I got the catted version of the DP is so that I will not have any issues with smog in the future. While having a cat converter passes the physical inspection, I have heard that in some states, with the CEL on, you might not pass smog.. is that true?

The addition of a cat on the CP-e downpipe is not exactly an inexpensive option, and with the sacrifice of more power, I would have expected the compensaton of no CEL just as Tufast had mentioned.
 

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Thanks for the quick responses, cjd, prime and Tufast.

Yes, I will have to say that the primary reason I got the catted version of the DP is so that I will not have any issues with smog in the future. While having a cat converter passes the physical inspection, I have heard that in some states, with the CEL on, you might not pass smog.. is that true?

The addition of a cat on the CP-e downpipe is not exactly an inexpensive option, and with the sacrifice of more power, I would have expected the compensaton of no CEL just as Tufast had mentioned.
While the addition of the cat is not expensive, there is a $2,500+ fine if you get caught without a cat on your car (federal clean air act). The cops in most states don't enforce this, but in places like CA where smog and pollution are at the forefront of community issues, you could be taking a big risk versus the little return.

If you have an iPhone, or an Andriod phone, there are seevral apps on the market that will turn your phone into a scan tool. You will have to buy an OBD2 bluetooth adapter, but they are not expensive ($50 and up). You can then reset the codes with your phone before you get the car's emissions tested. It usually takes a while for the CEL to come back, so if you do it right before they test the car, you should be okay, unless you live in a state where they do a visual inspection of the cat.

BTW, the app also lets you do data logging , and can turn your phone into a functioning digital boost gauge (among other things). I can provide more info if interested.
 

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Yeah, I guess even if I end up with a CEL, its better to have a cat installed. Besides, its a Hi-flow cat & shouldn't restrict power very much. Hopefully my custom tuning solution will take car of any CELs that would occur, if not I've got access to a scan tool.
 

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If you are worried about your CEL causing a rejection when getting an inspection, reset the ecu in the parking lot. The cel should not show up at low engine speed since there is very little air flow in the exhaust. Atleast it does not for me.
 

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never had a cel with my cp-e downpipe ..
 

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When you clear your codes the ecu stays in a state of "not ready" until you have driven a certain amount of miles at highway speeds to prevent you from just clearing you codes in the parking lot... You shouldn't get passed with a CEL or if the ecu is in that not ready state. Thats if they plug into your obdii port to check.
 

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I have not seen a CEL with my cp-e dp w/highflow cat ,been running with the dp for over half a year now
 

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Did you double check what code is being thrown? Make sure you don't have any exhaust leaks, double check 02 sensor clips, make sure 02 sensors are tightened all the way, etc.

If you went a couple weeks without a CEL and it just now started showing up, it makes me think something came loose or changed...
 

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When you clear your codes the ecu stays in a state of "not ready" until you have driven a certain amount of miles at highway speeds to prevent you from just clearing you codes in the parking lot... You shouldn't get passed with a CEL or if the ecu is in that not ready state. Thats if they plug into your obdii port to check.
Va doesn't scan if they do not have a reason to. Could be different in different states.
My CEL actually will go off when I idle for extended periods even after driving and sometimes when cruising....due to low exhaust flow
The car will be fine if you reset in the parking lot.
 

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Leaks large enough to cause sensor issues that close to the engine should be very audible. Shouldn't take you long to figure it out. Keep us posted
 

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If you are worried about your CEL causing a rejection when getting an inspection, reset the ecu in the parking lot. The cel should not show up at low engine speed since there is very little air flow in the exhaust. Atleast it does not for me.
wont work right away, sense you will fail for the ECU not being in ready mode
 

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I believe I'm going through the same issue your having. I have the o2 housing with hfc and recently got the cell after driving fine for awhile. Haven't been able to read the code because the shop I go to for some reason can't read the code and neither can autozone. Post back and keep us informed
 

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When you clear your codes the ecu stays in a state of "not ready" until you have driven a certain amount of miles at highway speeds to prevent you from just clearing you codes in the parking lot... You shouldn't get passed with a CEL or if the ecu is in that not ready state. Thats if they plug into your obdii port to check.
wont work right away, sense you will fail for the ECU not being in ready mode
That is crazy that they put a scanner on your cars during an inspection without there being a CEL on dash. Thank God I live in VA. If it ever got to the point where they had to scan your ECU (for no effing reason) during an auto inspection, I might just move back to SC where there is NO inspection.

Hey guy, I retract my previous about resetting the ECU in the parking lot if you live an inspection Nazi state. Works for me everytime. Always has.
 
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