Why Do I still have a CEL after installing 02 Bung Extenders?

prometheus036

So like the question states, I have a reappearing CEL light that came back on after installing my test pipes. I took the 02 sensors out before breaking the bolts on either end, and did not use an impact until I was hitting the topmost flange bolt coming from header to cats. I put in the 90 degree bung extenders, and also threaded in the 2 inch extenders onto that to make sure I had plenty of room for the sensors to be out of the flow of exhaust gas. It (the CEL) keeps coming back, and I'm not sure why, as they are out of the direct flow of exhaust gas. Did I make a mistake by putting the extra extender on? Should I only use the 90 degree extenders? Thoughts and opinions are greatly appreciated!

The codes are P2098 and 2096, voltages are at 0.290 and 0.280, which seem normal.

Also, I have some buzzing coming from the trunk/hatch area, around 3-4k rpms, is this normal? I've heard it comes with the territory of having RTPs and Resonated Axle Backs.

SonicVQ

Your rear O2 sensors need to switch between ~0.9 volts and ~0.1 volts to keep the ECU happy. If they are constantly at 0.28 - 0.29 volts they are too lean and the ECU will turn on the CEL.

Since the rear O2 sensors are now out of the exhaust stream from the extender/anti-foulers they don't "see" much of the actual exhaust and just the air inside the extender/anti-foulers. Air (or more accurately, oxygen) = lean.

On the newer VHR ECUs (2012+ ?) it uses the rear O2 sensor to check for an Air/Fuel sensor lean bias.

Here is a good video on what the ECU is expecting to see. If you know what it requires, maybe you can figure out a way to make the ECU happy.



I think most just get a tune and turn off the CEL or put back the cats.

prometheus036

I'm trying to avoid a tune so I can keep the warranty for now, once it expires I'll look to do that. I was under the impression that backing the O2 sensors out of the exhaust stream would trick the ECU into thinking the correct Air/Exhaust mixture was there. I've heard people say to use steel wool as well to bypass it. Does that actually work?

SonicVQ

^^^ I don't have a lot of data on this, but I think those tricks used to work on the G35 and older G37s.
PS the video above used a G37, so it directly relates to your car.

Can you try graphing or data logging the rear o2 sensor voltages and accelerator pedal to see how they respond with the "extenders"?

projectpanda

Have you tried using just the 90 degree or just the 2" extender? Maybe one of those would allow just enough to trick the reading.

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RHM 75mm TB & ported up/low mani., 3" intakes/velocity stack, Z1 Headers, Motordyne ART pipes, HBP 3.5" exhaust, Tein MonoSport, SPL F/R arms, endlinks, and tie rods , Eibach sways, Z1 rotors F/R, diff bush., subframe collar, Bell Raceworks diff brace