4DRZ

iTrader: (7)

I have a '13 G37S sedan with DC ceramic coated headers, Z1 high flow cats, and stillen exhaust. I was at a track day for Road America and drove all day without any check engine lights. About half way home the check engine light comes on. It is a code for the right bank cat not operating correctly.

I had some issues with heat while at the track day so I thought I might have melted the inside of the cat. Upon inspection it looks fine on the inside.

Has anyone else had this issue or know a solution? I am wondering if maybe the O2 or another sensor got cooked from the heat.

I can always have Z1 do a tune for me so it does not throw a check engine light, but I was planning to wait until I get their intake manifold and intakes. Anyone have the Z1 manifold or intakes and want to tell me what they think?

Thanks!

SonicVQ

I assume when at the track the throttle was mostly wide open. This means the ECU is in open loop and does not look at AFR/O2 sensor for feedback. (and fuel trims are 0)

However, when on the street it DOES mostly operate in closed loop and looks VERY carefully at the AFR/O2 sensors. You high flow cats are not working well enough for the rear O2 to give the proper switching frequency and duration.

The only solution I can see is a tune, to block the CEL.

4DRZ

iTrader: (7)

That makes sense about when it caused the CE light and the solution. The only thing that does not make sense is the fact that there were no CE lights for the first year with the cats and that included a few other track days. So if the cat is the issue, something changed with it at that track day. That cat looks fine on inspection. Do you think I melted something with the additional heat? (Straights at RA are a lot longer than the tracks I was at previously so higher top speeds and more heat)

SonicVQ

I think the cats are now not functioning as efficiently as they did new. On some cars, if the catalytic efficiency drops to the low 90s, it will set a CEL.

If you have access to a OBD scanner (bluetooth or Wifi and app for you phone)
post the Mode $06 data. (For Torque this is "Test Results") This will show what your catalyst efficiency is.

Also, if you data log the rear O2 sensor you can verify proper function.

MaQG37

iTrader: (4)

Clear the code, give it a few cycles and see if comes back after your normal day to day driving. It took about 2000 miles for my CEL to go away on my Fast Intentions resonated test pipes.

SonicVQ

If you clear the code, the freeze frame (engine conditions when CEL came on) and mode $06 data (like cat efficiency) is deleted. If possible, capture them before reseting.

The only benefit of clearing the code is to turn off the CEL light, which it may do on it's own if it passes the cat efficiency test the next time it's run.

MaQG37

iTrader: (4)

The light drives me crazy but you bring up a good point.

4DRZ

iTrader: (7)

Cleared the CE light last night and it has actually stayed off for a number of driving cycles. (It will probably turn on as soon as I start up tomorrow now that I mentioned it.) I also took a look at the O2 sensors on my tech's suggestion, but they both look fine.

Ape Factory

iTrader: (3)

You can't tell a thing by looking at the sensors unless there's been a catastrophic failure of a physical nature. Voltage range needs to checked along with response time. Would need a dedicated tool to do that like a picoscope (oscilloscope) and the proper software. Infiniti has the right tools I'd assume and the ECU is designed to send a code if something is out of range. I think an OBD reader might work but it also might not be accurate enough or have the right algorithm to read the 02 sensor's output slope (curve).

4DRZ

iTrader: (7)

I had a feeling I probably would not see anything on the O2 sensors. But after melting the rear ABS sensors, cooking the power steering fluid, and getting the radiator to spit at the last track day, I had a hunch there might be some heat damage. No dice.