[ruiningthegame]

About two months ago I got my exhaust installed by a guy who's a welder, and not really an exhaust shop. He was super cheap and had a lift, and did exhausts on the side. Well, one of the studs from the headers that connects to the exhaust snapped off and was stuck there. Instead of heating it up and removing it, the guy hit it with a hammer. And of course stuff that looked like sand was coming out of the Catalytic Converter. I bought a Circuit Werks full exhaust off ebay. Because of COVID my wife got furloughed for awhile and we had to use the money that I had saved for a proper exhaust system. He welded everything up and the job looked pretty good. But after turning the car off an on, I had the SES light.

The car is a 2013 e92 328i with the N51 engine. I got all the OEM heat shields and mounting points from a wrecked 335. Previously I swapped out the trunk storage so everything fits OEM wise. Before I got the exhaust I had a buddy (who's a mechanic by trade) help me move the evap canister and bolt it to the rear subframe so it was out of the way. I'm sure the purists will hate this, but my OCD wants things to be even, so to each their own.

I drove the car around for awhile and didn't notice the exhaust was touching the evap canister and melted it. I started getting codes for a leak and a notification that my gas cap was open. Then it melted even more and spewed charcoal pellets all over my garage floor. I then ordered from the wrecking yard a 335 and a 328 evap canister. Turns out they were both the same, and not the same as the N51 canister. So I made it work, and the notification for my gas cap being open went away.

While trying to fix the problem myself I bought both Post-Cat sensors and proceeded to put one in. The drivers side one went in, but wouldn't let me torque it down but seemed snug and wasn't coming off. The passenger side one, I couldn't even get it to loosen without hitting anything. Erased all the codes, turn the car on and drive it around. The code comes back and nothing has changed.

At this point I was pissed that I had basically ruined my car that was running fine before all of this. I ended up taking a hammer to the exhaust to make sure it would be nowhere near the evap canister. I am also tired of dealing with the significant loss in power and gas mileage. I took the car to a local shop that had good reviews on Google. We moved from Nashville to Orlando, and all I can say is that I miss German Motorworks. If you are in that area those dudes are the best!

The shop took in the car and said they scoped it. I had to grill them for answers since they wouldn't ever call me (a sign of a bad shop). They put in the other Post-Cat sensor and said they torqued the other one down. The scope apparently showed that the plug that connects into the plug for the sensor was bad. They said they ordered the wiring harness and were going to install it. I also asked for an alignment. Since the car was driving like crap when the guy that did the exhaust had to unbolt the passenger side rear subframe bolt to get the exhaust bracket from the 335 to go on.

After them having my car for nine days, I called down and said I was going to come down and see what was going on. Later on in the day they called me and said that they couldn't fix the problem and that my ECU was bad. The didn't charge me for the labor or part and only charged me $145 as a diagnostic fee. However, they didn't do the alignment and there are no clipped zip ties in my engine bay (cowel delete and BMS cabin filters installed). Which tells me they didn't actually put the harness in, just removed the cap covering the ECU. So it seems as if I gave them my car to only put in that other sensor (which they didn't even give me my parts back). Basically I got my car back in the same shape I brought it in, just dirtier with hand prints all over the body of my car.

Now that you've read my lengthy back story, I am asking what I can try to do to fix this? I've searched a lot for this issue and regularly find that people have replaced the sensor and it's fine. I did happen to find a post on another website (as of writing this) that it could be a fuse is blown for the sensors. But that is the only thing different I've seen other than valve cover/air intake manifold leaks. Which I can say for sure I don't have a valve cover issue since I replaced the seal myself after another shop in the Orlando area screwed me (surprise, they had good reviews too). The other thing I've considered is the AA Headers and the Tune to go with it to delete the cats completely since there is no emission testing in Florida. But I doubt it actually fixes the issue, and just makes the code disappear. The Codes in question are P0036 (post cat sensor), P1449 (DMTL), and P0442 (EVAP Small Leak).

For those looking to do this mod on their 328, I would say don't do it. I also didn't get the tips I wanted put on because he didn't have time and the stock ones are touching my carbon fiber rear diffuser and melting it. So there goes $250. The whole thing has been a headache, and yes if I could go back I would have just put a performance 328 exhaust on and called it a day. This is a daily, it now sounds like crap and runs like crap. So I've learned solid lesson in all of this.

[E92William]

Is the sensor that you replaced bank 1 or 2? The code is for bank 1 and it mainly says I believe that the heater circuit in it is screwed though your cat might have been damaged by the knuckle head that you had bang around that exhaust manifold. Did the shop replace the other one? As long as the primary o2s are reading fine the rear ones shouldn't cause an issue. I'd actually propose to get headers and a tune that takes away the stupid light for the cats.

We did a 3 stage manifold swap on a forum members e92 and we kept getting o2 sensor codes what happened was we pinched the o2 wiring behind the manifold and had even torqued it down it kept throwing codes and blowing the o2 sensor fuse I believe 35 or f79. It's one of the center ones in the fuse box you're going to see rows of 3 green 30 amp fuses mine was one of them the middle one

I've wanted to do that 335i exhaust conversion for quite a while but I simply don't feel like dealing with all the stuff that has to be moved around unless I were to find a parts car and dirt cheap parts to do the job. It does sound pretty damn well in the videos I've seen though!

[ruiningthegame]

It's definitely Bank 1, Sensor 2. The car drives differently after I took it to the shop. So they must have replaced Bank 2, Sensor 2 as well (like I asked them to). Which means both have been replaced and still didn't fix the problem. I am getting that same problem someone else in the forum had where the voltage on that sensor stays the same the whole time. And it's only the Bank 1, Sensor 2 that is doing it.

That's why I think it's the fuse at this point. I was planning on getting the headers and tune anyways. But this is my daily, and to spend $1400 on them my wife will kill me. But I guess, ask for forgiveness... lol. I'm going to look at the fuse box today and see if anything is blown and I'll let you know what I find. Being told that I need a new ECU is a bit ridiculous.

The exhaust conversion isn't too hard. Especially if you don't have an N51, you can move the evap to under the drivers side rear bumber (where it goes on the 335). I was recommended a guy from some people in the car scene here in Orlando that has a wrecking yard. I paid $120 for all the heat shields, mounting brackets, bolts, basically everything. It all fit perfectly! I would say this, don't have some guy bang on your headers and also don't have him weld it up on the car maybe. So you don't have to deal with my problems and you can enjoy your dual exhaust.