Before i got the exhaust installed i browsed a hand full of threads and majority of them stated that they used oem gaskets so i had bought new oem gaskets for them to use in place of the larger invidia gaskets that go up front. Hopefully they still have the invidia gaskets to use if that is the issue.


Separate question: on the intake tube what are those two ports that stick out? I saw that the rr racing intake does not use them. Are they really not necessary?

 

P0420 is for catalyst system, bank 1. So this is the downstream O2 sensor on passenger side. With the Invidia exhaust, poor installation will cause an exhaust leak at the header connection, which will definitely trigger that code. Most recommendations are to buy new OEM gaskets. Not using the OEM style gasket at that front connection seems to be the only issue with this exhaust, some guys get a code right away, others go a long time with no issue (10k on mine, used Invidia gaskets, no problem). The Invidia comes with two different sized 2-bolt gaskets, the larger one should be used at the header to exhaust connection, the smaller ones are used at the x-pipe connection. These style gaskets are always "sloppy" so it takes effort to ensure they stay centered while tightening up the exhaust, some guys just rush it sometimes. It's possibly the sensor wires were damaged during removal/installation, but by far the gaskets are the most common problem.

Replacing/fixing the gasket will fix your code issue.

Some additional gee-wiz info based on other (incorrect) replies so far: each bank (side of the engine) has two O2 sensors. Upstream (sensor 1) is a wideband O2 sensor that the ECU uses during closed loop for A/F ratio adjustments. This one is in the header, before any catalytic converter. Downstream (sensor 2) is a narrowband O2 sensor, located after the catalytic converter and measures the efficiency of the cats (aka emissions).
The RCF has 2 sets of cats, one in the headers, and another down in the exhaust. Most cat-back exhausts delete the second set, but because those cats are after the O2 sensors, they aren't monitored so no codes will be triggered.
Simple closed-loop explanation: the MAF measures how much air is coming into the engine, magic happens in the ECU and it adjusts the amount of fuel the injectors spray in order to target a specific A/F ratio, the ECU then monitors the upstream O2 sensors to verify the target ratio was reached, if not it makes minor adjustments to the fuel tables until it reaches the A/F target.

 

OK, I'll admit, I've only been under my RC F to perform oil changes and haven't done anything with the exhaust, but I'd like to clear up some of terms being used.

O2 Sensors. The front O2 sensors (before the cat), one on each bank, measure the air/fuel ratio leaving the engine. Their voltage output is sent to the ECU where it calculates and adjusts the air/fuel ratio. The rear O2 sensors (after the cat) measure the air/fuel ratio to determine the effectiveness of the cat. So the front O2 sensors are responsible for engine performance and the rear O2 sensors are responsible for catalytic converter performance.

MAF Sensor. The Mass Air Flow (MAF) sensor is usually mounted on the intake manifold and measures the amount of air pressure in the intake manifold. The MAF sensor sends the barometric pressure reading to the ECU for air/fuel ratio calculations, which is important when you drive in mountainous terrain or drive at elevation.

IAT Sensor. The Intake Air Temperature (IAT) monitors the temperature of the air entering the engine and is usually mounted on the intake tube. The ECU needs the IAT data to estimate air density so it can adjust the air/fuel ratio.

As you can see, all three sensors play a vital role in ensuring the ECUs send the correct amount of fuel to the injectors based on observed sensor data.

EDIT: Oops, didn't see LoSt180's post until I posted mine. BTW, nice post LoSt180.

 

From what I remember, I felt the OEM gaskets were a bit too small considering how much larger the Invidia piping is. The important part is to ensure the gasket stays centered on the Invidia piping as things are tightened down.

Those ports are for the PCV system. The rr-racing intake includes some extra hose and an external filter for the PCV system. My guess is they didn't want to mess up the look of that pretty carbon fiber with adding some ports. Personally, I'd like to keep everything hooked up as OEM as possible. With a free air breather (like rr-racing) there's a chance un-metered air is entering the engine, messing up air/fuel ratios. In reality, it's probably a non-issue, but I'd rather not take that chance (favoring reliability over max gains).

 

Lost180 and Phinatic, thanks for your clarification posts in helping the OP try to identify and resolve his CEL issue. As many of us have seen in the past, throwing that particular CEL after an exhaust install is not totally uncommon, and is usually a simple fix once the problem has been diagnosed and gaskets installed correctly. Rolla also addressed this in his reply so thank you to him too.

Yri, thanks for editing your post. You're a valued member of the forums and we appreciate your participation, but please try to refrain from guessing and potentially spreading bad info. I know you don't yet have an RCF and are still shopping, and some of the things that come up in here can only be known by those who have worked on, owned or extensively driven an RCF. This is a great forum to learn more about the car, and let's keep it that way!

 

Thanks dude. i’m taking the car into the shop in a few minutes, ill pass on the tip and tell them to remove the oem gasket and use the invidia ones this time around if that ends up being the issue.

 

So in a sense I was correct. I call the wideband O2 sensors "A/F sensors"... and the narrowband O2 sensors.. well I call them O2 sensors. So, if I understand correctly, there is 1 wideband O2 sensor per each bank, and out back after the first set of cats there is 1 narrowband O2 sensor after the header cat, that measure how well the cat are filtering the exhaust. Thank you for clarifying the situation!

 

I ordered new OEM gaskets also after reading various threads, but it was pretty obvious the OEM gaskets would not seal correctly with the new Invidia exhaust. I used the new gaskets that came with the Invidia exhaust and have had not issues with CEL or leaks.
I have some new OEM gaskets if anyone needs them.

 

I wish someone came up with the "perfect" gaskets for the Invidia cat-back in the RC F. I originally got a CEL with the Invidia gaskets, so switched to OEM gaskets but CEL returned a few hundred miles later. I put on new OEM gaskets (they are pretty inexpensive!) and thought I was finally done with the CEL. Thousands of miles later the CEL is back on (same P0420 code)... . By the way, in the 2UR-GSE, Bank 1 is on the driver side, not the passenger side (US-spec). The attached Lexus Service Bulletin clarifies this. Enjoy the Invidia... despite the CELs, it is a great option for the RC F!

 

shop just let me know that the oem gasket was the problem and they sealed it with high temperature silicone and marked to try using invidia gaskets next time.

damn so neither way worked for you. Thats annoying. Like you said though, still an awesome option and still loving it. If i get that code again, is it safe to drive around with and still drive aggressively or is it something i need to get addressed asap?

 

There are many of us who have had ZERO issues with Invidia for years. We used the supplied gaskets with the Invidia and never any CEL. Just trying to spread some optimism.

The only things I knew to be cautious about was the O2 sensor and the gaskets being used in the right place. Since they both are so close in size, it is easy to switch the front and rear one's and that causes a leak.

 

Maybe I just got lucky, but the gaskets that came with the Invidia exhaust seemed to be very good quality. I did take the time to clean and smooth the header pipes where they connect to the Invidia exhaust with a wire brush and file so that the gasket laid perfectly flat. I also took time to make sure the gaskets were aligned properly by connecting the entire exhaust loosely, then tightening starting at the front and working my way back. There was some wiggle room for the gaskets to move when tightening. It would drive me crazy to use silicone to seal my exhaust and there is no way the OEM gaskets would work on the Invidia exhaust. I should have taken pictures of the gaskets, but I was in a hurry to go for a ride.

 

oh yeah for sure, its a forum so i know there will be more complaints about something rather than people saying their product is working as intended. Im sure most people dont have this problem. I still dont regret my purchase and would do it again. Stuff like this doesn't bother me much. Get it fixed and continue on with life

No worries. They will keep the gaskets on hand for me if it happens again. We’ll see how long the silicone holds up for. Im happy to have the car back so i can hear the exhaust note again

 

This
I bought my Invidia used and sourced the gaskets on Amazon and OEM Lexus. IMO the OEM ring gaskets are too narrow in diameter to fully form a barrier where it mates to first Invidia pipe. I did not use the OEM gaskets for that reason and used gaskets sourced on Amazon. I believe this is the one I used and it works well. No CEL yet.

 

Thanks for this info, will definitely save this link!