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Can CFM HFC cause me to throw a p0420

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EuroAyres

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Discussion starter · #1 ·
Just like title says. Everything is fresh and smooth but I keep getting the p0420. Turn it off, and it's back In 40 something miles. So I'm wondering by worrying my emission with a HFC is that a reason. Also is it hurting performance and how to rid it. I hate dummy lights on. Lol.

Thanks
 
#2 ·
Yes a high flow cat can cause a p0420. The rear o2s job is to monitor the cat. If you a high flow one it will see that the. Atalyst isn't in spec and will throw that code.

Only way to get rid is to put a "cheater" on it or get a tune that will change the specs. In my opinion get a tune your engine will love you for it.
 
Discussion starter · #4 ·
I want the tune. From who though cause I also have a fully ported and polished head, svt header, cfm 2.5 flex, and the FS race exhaust. And a k&n in stock air box. How much do they run and can u still just get a mil cheater in case I don't want to pony up for tune for now. The biggy is am I loosing performance?

Thanks
 
#5 ·
The downstream sensor doesn't change the fuel trims, so no, there shouldn't be any performance loss. As LDS said, it's simply there to monitor the catalyst. You can grab a cheater or non-fouler if you just want to get rid of the CEL/code. As for the tune, you should definitely try to get one as soon as possible to get the most out of your mods that you have. Talk to Randy to see if he can help you out over at FSWerks.
 
#6 ·
Mindstorm20 said:
The downstream sensor doesn't change the fuel trims, so no, there shouldn't be any performance loss. As LDS said, it's simply there to monitor the catalyst. You can grab a cheater or non-fouler if you just want to get rid of the CEL/code. As for the tune, you should definitely try to get one as soon as possible to get the most out of your mods that you have. Talk to Randy to see if he can help you out over at FSWerks.
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No.

It does change fuel trims. In fact it will do everything it can to get the catalyst functioning correctly and until it does it will not run standard fueling maps.

As long as there is a mil for catalyst efficiency, there are driveability variances.

- Drew
 
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#7 ·
Hmm, that's the first time I've ever heard of the downstream sensor doing anything other than providing the ECU with whether or not the catalyst it operating within a set range of efficiency. I was always under the impression it did not cause the ECU to adjust fuel trim.
 
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#8 ·
svtf02red said:
Hmm, that's the first time I've ever heard of the downstream sensor doing anything other than providing the ECU with whether or not the catalyst it operating within a set range of efficiency. I was always under the impression it did not cause the ECU to adjust fuel trim.
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It is capable of getting the ECU to adjust to try and correct the error within a small window. If it can not adjust to fix the issue within the parameters it will throw a code, and in very bad cases it will force the CEL to flash. But this is a VERY limited set of parameters.
 
#9 ·
Interesting, I have mine unplugged for testing reasons, and it hasn't changed the trims or timing any noticeable amount. Is this only if it's plugged in and showing the catalyst is being burnt? (i.e. super rich)
 
#10 ·
Mindstorm20 said:
Interesting, I have mine unplugged for testing reasons, and it hasn't changed the trims or timing any noticeable amount. Is this only if it's plugged in and showing the catalyst is being burnt? (i.e. super rich)
Click to expand...
Yes, it's smart enough to just throw a code and be done when it is disconnected. It's when it IS connected and it ISN'T reading within spec that the ECU can get "worried". But as I've said, this is a VERY small window and usually the sensor is just dead by the time it can get in that window.
 
#11 ·
That's good to know, I was unaware of that.

Thanks! :thumbup:
 
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svtf02red
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