truegeek

I'm no Gear Head but I have just got told something that is really hard to swallow for me. I have put almost 18000 miles on my Boss with Zero mechanical issues. Until today. On the way to work CEL comes on. I by chance already had an appointment for later today for them to look at my drivers seat that looks like it has 200000 miles on it, so they said they would look at the code.

They did not tell me the code number but said something about "cat converter below efficiency". They cleared it and said it was probably due to me having put in a K & N Air Filter. NOT a CAI, just the filter.

My only mods are Tint on the windows, K & N If you call that a mod?, and the side pipe cutouts.

Can someone please explain to me how that could possibly be caused by the air filter? As I said I'm no Gear Head and I know a few of you are and a few more think they are.

nota4re

Hey Jeff,

As you suspected, they are wrong. This particular code is part of the Federal OBD2 requirements for all post-1996 vehicles. OEMs are required to have sufficient on board capability to test and detect catalytic efficiency and, further, the ability to display and store a code for the operator. In short, the OEM has to be able to tell you when your CAT(s) need to be replaced. 99.9% of all of the cars manufactured since 1996 have O2 sensors before and after the cats and the use the downstream sensors to compare to the OEM sensors and over the years, they more or less perfected this detection capability. The new Mustangs are different. Instead of O2 sensors ahead of the cats, the new Mustangs have true wideband sensors. (For the most part this is VERY good, in that it allows the ECU to make adjustments based on PRECISE air/fuel readings.) Aft of the cats, the Mustangs still use "ordinary" (aka, lower cost) O2 sensors. Now, the ECU programming algorithms need to be different to compare the wideband readings to the O2 readings and to know when to display a code corresponding to catalytic efficiency.

Hopefully, and most likely, you had a one-time glitch. A bad batch of fuel could be one of the causes. However, it wouldn't surprise me at all if there's an ECU update in the future on the Boss cars - if not all 2011+ Mustangs. I say this because our experience is that we KNOW the catalytic efficiency test is very finnicky on the Boss cars. We have been working with Kook's on cats that will work with their headers. At one point we had some large cats on the car that work absolutely fine on the 2012 Mustang GT. Further, we strongly suspect that these cats would be sufficient to pass CA Emissions tests. However, the Boss ECU would continue to trigger the CEL with a catalytic efficiency code.

Sorry for long answer. I hope a glitch. If not, your emissions warranty is good for 80,000 miles so it is on Ford's nickle to fix!

truegeek

Thanks, I know there are tons I don't know about cars but their answer just could not pass my sniff test. I hope you are correct about the one time glitch.

Again Thanks for taking the time to completely answer my question.

RJorge1950

Hi Kendall,

Do you know of a cure for the CAT CEL ?
I would like to put a race pipe (for track days only) and not see a CEL.

Rob

nota4re

Historically, CAT Efficiency CEL have been easy to eliminate. You simply use an SCT or similar programmer and supress this alert. This is still very possible on the Boss, but if you have or plan to get Track Key, then you can't do this without backing out the TK capability.

For track events without CATs, I would just let the CEL come on and every couple of sessions you might get in the habit of spending 30 seconds to check the codes to make sure nothing else is going on.