Can someone explain to me the CEL for a bad cat? So the shop tells me I need a new cat. I looked on here and others are reporting cat failures in the 20s, so everything jives well there. They quoted me two new Ferrari Cats and I coughed a little bit. Even top brand aftermarket performance alternatives are cheaper, so I was going to go with one of them. the challenge with a lot of them is how long will they make it before failing. So I thought, wouldn't it make more sense to go catless? Searching the forum there were others concerned about the "CEL", but then I read specifically on here that the 360 won't throw a CEL. The reason that confuses me is because how do I get a CEL for a bad cat, if no cat would not throw a CEL. Wouldn't it cause the same issues as a failing/ burnt out cat? Quite confusing. My understanding is the reason I'm getting a CEL is because the Catalysts have burnt up in the cat. A catless pipe wouldn't have anything there at all, so it would be just like a cat without the catalysts. If anyone can either school me on how the cat-based sensors work or why a catless set up won't throw a CEL, I'd greatly appreciate it. I just find it somewhat confusing.
Let me make it as simple as 2+2... The sensors are looking for a reading that shows that the catalyst is functioning within a given parameter... If there is NO catalyst then the sensors would not report a reading within the set parameter. The same goes for your faulty catalyst. It is producing a reading outside of the set parameters. Both conditions will set a CEL.
Thanks a lot. That's exactly what I'd expect, which is why I was so confused by explicit references in this forum that it wouldn't (but that the 430 would). Still odd so many people said it won't. Thanks for confirming.
If you're deleting the cats entirely, instead of replacing with a performance after market, there's no place to plug the downstream O2 sensor into, so that gets deleted too, I would think. If that sensor is disconnected or removed, nothing to trip the light? Not certain, hence the question mark...
I think its a little different for a US 00+ car, vs a US 99 car... on the 00+ cars the pre/post sensors look to me to primarily measure the pre-cats rather than the main cats of the car. The rear sensor is kind of in the middle of the main cat, so I think does measure its efficiency to some extent too.
OK I was 100% on board but now I'm reading there's no sensor AFTER the rear cat. If theres no sensor after the rear cat then there's no reading to take and therefore it can't be triggered by a faulty cat. The sensors are after the precats, which means they are really measuring pre-cat efficacy, which are in the exhaust manifolds. That therefore makes sense why the cats couldn't throw a CEL, because its the pre-cat that really functions the catalyst process your discussing.
I think the main cat is really a two cat unit on each side, with a sensor in the middle. If that is correct, I would wager that removing the main at would result in a reading that is out of range. Sent from my iPhone using Tapatalk
I wish there was more definitive information, but you are probably right. I pinged someone who sells them as well. I'll report of I hear anything different than what you are suggesting. Thanks!
Ricambi parts diagrams are excellent source - sensors are 16 and 17 EXHAUST SYSTEM - Ricambi America, Inc. Two sensors per cat and since they're part of emissions if you disconnect you'll get a CEL.
PO removed the OEM Cats (I still have them, and others who do may wish to sell theirs) and replaced with Cat Bypass/Delete Pipes. I get no CEL but do get a SlowDown on startup occasionally. Goes away in 30 sec. or less. Pipes have extended sensors but still its thinking the Cats are overheating.
I went cat delete and got instant CEL. Changed to Hyperflow sports cats and no more CEL. Sounded better too.
Here's a question: If you plugged that second downstream 02 sensor bung and just had the sensor outside the airflow so that it was reading clean air, would that trigger a CEL?
I'm Using mini cats they work. Simple fix for CEL issues with no cat. <title>O2 Simulator Mini Cat Cel Fix best oxygen sensor simulator made. Also add a 3rd 02 bung next to the upper one and add an Innovate LC1 or the new LC2 to log you AFR. http://www.innovatemotorsports.com/products/lc2.php
That's not true for everyone. I have Fabspeed mini cats and with their headers and sport cats, I get a CEL. So, back to my question or, if you prefer: What would happen if you took that mini cat and welded it closed, so that the 02 sensor was completely isolated. Would it trigger a CEL because the air is too clean ?
That's a good question. They sort of shrugged it off and said they can't prevent a CEL with their headers and sport cats in tandem (although had I known that before I would have stuck with the stock cats and only bought the header). Even with their mini-cats, which I bought thinking that was indeed the solution.
Michael B is correct. With OBDII came post cat O2 sensors to monitor the function and health of the CAT. So, if a CAT fails, a CEL is thrown to alert you and also not allow the car to pass inspection. If you remove the CAT's and install test pipes, you need to fake out the sensor. 200 cel hi flow aftermarket CAT's are often a great choice and won't throw a CEL (depending of the manufacture)
Remove the post cat 02 but keep it connected and plug the hole see how you go, the pre cat 02 will still read the AFR and trim. Leaving the post cat 02 to atmosphere will still keep it in play.
I"m thinking of doing that. If it works, I"ll make some extenders that are plugged and isolate the sensors. However, that's such a simple solution, there's no way that I'm the first to think of it and if it works, why hasn't someone made plugged extenders before? I would think there would be a great market for those instead of all of those hit-or-miss extenders.
I highly doubt this will work, Ryan. Someone that knows more about the sensor dynamics than I can probably post why.
If you have headers and cat bypass pipes you will through a cel. The main 02 sensor mounted upstream of main cat and the secondary 02 mounted downstream must sense a electrical difference in order to make adjustment to the exhaust gases. Removing the cats there isn't anymore a difference between the two therefore the signal they send out is the sametelling the main ecu that there is something wrong with the cats. I have a 360 spider that mounts fabspeed headers cat bypass and capristo level three exhaust and nothing worked (02 extenders big daddy Mini catsand other gadgets). The only thing that worked was seeking the help of Steve mase at mase engineering located in Jacksonville fl. He took my main ecu and disactivated the part of the software program related to the emission cel.the cel related to engine problems proprietary to Ferrari was not effected. No more cel for over two years. Give him a call. If you still have cats in your Ferrari this isn't the solution for you.
I've got OE headers, 100 cell Agency power cats and Tubi exhaust. I've tried the mini cats and different spacers etc etc and still keep getting a CEL. It's driving me crazy.. Out of desperation I tried what you're suggesting. I pulled the post cat O2 sensors out and zip tied them out of the way and plugged the bungs. Cleared the code and crossed my fingers. I got a CEL again very quickly. I didn't read the code but from what I've researched it would be P0140 - 02 "No activity detected". Save yourself the trouble.. :/
Dynojet do 02 eliminators that basically give a reading from the heater wires and the ECU thinks the 02 is connected. I've not had a problem with CEL on my cars but if I did it would not take me long to fix it without the need of touching the ECU by going through this type of system or resistor/capacitor like in the link in my last post.
