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Old 12-01-2009, 07:42 PM   #1
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New to the forum. Completed install of BEGI turbo/IC (7psi boost) and EnthuzaCar exhaust (including downpipe with Cat) in September. Car runs great (no misfire, no ping, etc). Last week for the first time, got a CEL that persists resetting and mechanic says p0420 code means non OEM Cat and he has no solution short of "get used to it". I'd really like to get the CEL off on a more permanent basis. Jason at EnthuzaCar suggested posting question here. Any ideas? Thanks.
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Old 12-01-2009, 07:53 PM   #2
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It might help to know what year car you have.
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Old 12-01-2009, 07:57 PM   #3
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Get rid of those crappy band aids and get a real engine management unit. Problem solved
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Old 12-01-2009, 08:11 PM   #4
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Sorry. It's a 2002
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Old 12-01-2009, 08:16 PM   #5
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Get an Adaptronic
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Old 12-01-2009, 08:36 PM   #6
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Pickleking, read my post here: https://www.miataturbo.net/forum/t29945/#post348921 .... works great. My car is a 2004 so the wire colors should be identical to yours.
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Old 12-01-2009, 11:03 PM   #7
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Quick before someone gets their chones in a bunch. Post in the noob section and denoob your self. For your own sake heed this warning. Also learn to use the search function it is a great help. There is also Miata.net that has tons of info. Between the two sites you can have a solution to just about any question you may have.

Welcome and enjoy. Some will bite prior to asking questions. However this is a good bunch of people.

Have a great day,
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Old 12-01-2009, 11:12 PM   #8
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Jared - Thanks for your concern. A search of this site and Miata.net, which I have belonged to for several years, yields no information that is useful to my inquiry. Maybe one of the helpful folks here will suggest something.
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Old 12-01-2009, 11:29 PM   #9
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Quote:
Originally Posted by Pickleking View Post
Jared - Thanks for your concern. A search of this site and Miata.net, which I have belonged to for several years, yields no information that is useful to my inquiry. Maybe one of the helpful folks here will suggest something.
Did you read what I posted above? My fix for your car's problem is cheap, easy, and foolproof.
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Old 12-01-2009, 11:42 PM   #10
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Yes I did and thank you for it. If no other suggestions are offered, I intend to pursue it. Thanks.
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Old 12-02-2009, 12:11 AM   #11
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The thing is, that CEL code doesn't mean there is anything wrong with your cat or exhaust, it just means your cat or exhaust is less efficient (a.k.a. "better" in performance terms!) than what your ECU expects.

The only way to "fix" it is to put in some restriction (like a crappier cat/exhaust) or to change the input that the ECU sees. My way does the latter.
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Old 12-02-2009, 12:20 AM   #12
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Thanks again. Have already sent the post to my ace mechanic, who has considerable experience with Miatas and, in fact, races them.
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Old 12-02-2009, 12:59 AM   #13
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LOL, it doesn't require a mechanic. I am a mental midget when it comes to working on cars, and a fumbling fool with a soldering iron. Yet even I got this to work in 15 minutes. If you were in New Jersey, I'd come over and do it for you.
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Old 12-02-2009, 01:17 AM   #14
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I used an O2 simulator that I bought from O2 Simulator, E-commerce
Then I took an old O2 sensor from the junkyard and cut the pig tail off and soldered the simulator in place so it was total PNP. I think that website also has wiring diagrams, if not, ask me and I can provide. I was having the same problem when I first went turbo, as I no longer had a cat.
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Old 12-02-2009, 09:37 AM   #15
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I bought an O2 simulator for my '96 and never used it. $5 plus shipping if you need it.
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Old 12-02-2009, 01:02 PM   #16
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What evank suggests, works. You're other option is to offset the O2 sensor another 1/4" to 1/2" from the pipe. But that might throw a different CEL. So, do the resistor mod. We've done it before. It works.

https://www.miataturbo.net/forum/t29945/
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Old 09-15-2010, 06:22 PM   #17
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I hate being this guy, but I am going to him. Has anyone found out how to fake the heater circuit so that check engine light will not come on?
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Old 09-16-2010, 12:33 PM   #18
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We have a new device that will work well. It has worked like a charm on two MSM's so far. It is not our design, but one that a customer gave us to try. But we can build it, give me a call or shoot me an e-mail to discuss details.
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