Error code 0420?

What are parts 5 and 9 in the second picture, they're being labeled as rear catalytic converters on other sites, and on Amazon when I'm going to look for prices on replacements, they bundle them all together so you get 4, calling them the bank 1 front and rear catalytic converters, and bank 2 front and rear catalytic converters, and other sites are calling them primary and secondary catalytic converters.

For example.

Somehow, I missed the last part of what you said, addressing part 5 and 9, are you sure they're just exhaust tubing, because they're being labeled everywhere else as rear or secondary catalytic converters.

Yeah, I don't know, that doesn't seem to be right, are you sure it's for a 2011 Frontier 4.0? I added 2 more pics from the Nissan website, look at number 7 and 8 in pic 1, pic 2 shows what they are, they call it "converter and pipe" which I assume is short for "catalytic" converter and pipe, maybe your manual is shortening it even more and just calling it pipe, or doesn't account for the fact that they actually has a catalytic converter in it as well.

I clicked on the part itself and saw the other names include "front pipe" or "tube exhaust front", as well as "catalytic converter", I'm thinking because the part normally in that spot is called "front pipe" or "exhaust tube front" typically, but this one just happens to also have a catalytic converter in it as well, so it's 2 parts in 1 and can be called either or both. I attached a pic where it says it's other names.

Yes.

Awesome great thanks, and will do.

Sorry, I forgot to get back to you on how it went. I just went ahead and replaced the front converter only, and it seems to have fixed the issue. Also while I was at it I removed the back converter to make it easier to remove the front one, and while I was at it I looked inside it to see if it was indeed another converter like I thought, and if it also looked dirty, and it was indeed a converter, and the cells looked much cleaner than the cells in the front converter, so I think I won't have any issues with not replacing the rear one. The only problems I encountered were when removing the exhaust manifold cover the bolts were very tight and 2 out of the 3 of them snapped inside there holes, luckily, I managed to get 1 off without it snapping so it still has 1 to hold it on there snug enough. And the other problem was after several hours of driving it I started getting a pa200 error code, for faulty wiring in the front 02 sensor, which is the one on the converter I replaced, and I figured I might have pulled a little to hard on the connector without holding tight enough on the back piece due to it being difficult to getting both hands in there with one of them around on the back connector to squeeze the release flap while holding the back connector tight so the other hand could pull to unplug the front connector that's connected to the 02 sensor, I did feel a little something like that when I was doing it, like a slight give or pop, like one of the wires might have been pulled out of the back of the connector a little bit, so I wasn't too surprised when I got the code. But I got back in there yesterday to try and see if I could see if any of the wires looked to be pulled out at all, all that I could see was one of the rubber rings that go around the individual wires in the holes where they insert into the back of the connector was sticking out slightly more than the others, by like 1mm, so idk if that was it, it was very slight, but I did my best to push the rubber ring back in with my thumb nail, and also tried pushing all the wires back into the back of the connector the best I could with the limited access I had, again it's hard to get your hands in there, especially around the back side of the connector. But I've been driving it around all yesterday and today and haven't gotten the code again, so I think that might've taken care of the problem.

I take it back, the pa200 error code just came back up. So as soon as possible I'm going to try and unplug everything the harness connects to on that side of the engine so I can pull it up through the top and get a better look at it and see if I can push the wires in properly, or fix the ends of the wires somehow, perhaps one got dislodged from the pin that crimps onto it before you slide it into the connector.

Sorry I said pa200 but I meant p2a00, which is for bank 1 sensor 1 o2 sensor out of range, and it stuck in my head as bad wiring because that was the one of the causes that I thought it was, because I just replaced the o2 sensor, and because I felt that popping feel when I was disconnecting it like I said. But after looking back at the causes again I remember the other causes it mentioned such as a blown fuse in O2 sensor circuit, low or excessive fuel pressure, vacuum leak, or exhaust leaks. I know exhaust leaks would make sense since I just replaced the catalytic converter, but I tightened everything pretty well, but I'll try and see If its leaking exhaust somewhere, not sure how though, might just spray the joints with soapy water or something to see if I see bubbles, unless you have a better idea. I'll also check the fuses and fuel pressure and see if I can find any vacuum leaks. I'm actually thinking it might be a vacuum leak because I recently removed the intake manifold, so maybe I didn't replace one of the hoses securely enough, or one might've been old and started to crack, so I might check that first. If you have any suggestions let me know.

Hey, sorry it took me a while to reply, I hadn't gotten a chance to work on the truck till yesterday. I checked for vacuum leaks and couldn't find any. I tried to check my fuel pressure, but there is no easy access pressure port, the only way other than lowering the fuel tank and checking it at the fuel pump, which is in the fuel tank, is to disconnect the fuel line where it attaches to the fuel rail via a quick disconnect connection, however I'm having trouble with that. I know normally there is a ridge on the male tube that the prongs inside the female quick disconnect connector latches onto so that you need a quick disconnect tool to remove it. I have a set of those in different sizes, but none of them work because there seems to be a second ridge on the male pipe, right outside the edge of the female quick disconnect connector, preventing me from sliding the tool under or inside the female connecter to compress the prongs so that I can release the connector. At first I thought maybe that was the ridge that the prongs were supposed to be catching, and that I must have released it already and that the pipe is just snug in there and I just need to pull a little harder, but I didn't want to pull too hard and break the prong, plus when I pull it you can hear the prongs catching on a ridge inside it, and it wiggles pretty freely until it reaches its stop and stops solidly, making the clicking noise of the prongs catching on something that must be a second ridge, so it's not like I got it passed the ridge and it's just on the pipe snuggly. I've also tried wrapping the tool around the ridge but when I do that the tool isn't flush enough with the male pipe to get under the female connector, it's either flush with the pipe but before the ridge so the ridge stops it, or around the ridge so it's not flush and can't get inside the connector. I've tried with all the sizes of the tool and can't get any under there. I've also tried, as I've read others suggest, to push down on the connector while pushing up on the tool, so that the prongs aren't in a bind with the ridge inside when I try to get the tool in there, but that isn't working either. I provided a picture to kind of depict what I suspect the situation to be, and a video where you can see the ridge that's outside the connector, blocking me from getting the tool in there, as well as how I can wiggle it and the noise it makes when it catches on what I assume is a second ridge. Here's the link to the video if it's easier: https://youtube.com/shorts/CKNEn_609Z8. Also do you have instructions for testing the throttle body, or a wiring diagram and the proper ohms or voltages I should be getting for each of the wire connectors prongs, I'm having trouble finding the info for my throttle body.

Similar but mine are metal, I have several in different sizes, I attached a picture of one of them. Try as I might I can't get it under with the ridge in the way.