E46 Fanatics Forum banner

P0153 P0174 codes (solved: clogged CATS)

1644 Views 28 Replies 4 Participants Last post by  bluetech
Hello everybody I am reaching out to the community for some help on codes that are on and off on my 2004 330ci with 269,000 miles. I have been dealing with especially P0153 and P0174 on and off again for about a year and a half now. Sometimes I get also a P0302 engine 2 misfire code together with the P0153 but that hasn't happened since this last spring.

I have tried look this up to figure what could be causing these codes, have replaced a few parts already and took it to a shop which specializes in German cars which I am at the point the common solutions have not fixed it. I have gotten the OBD fusion app and followed the link to download the three logs if somebody could please read them and help with a direction with the issue. I have it attached to this post.

Just wanted to let you guys know of parts that I did change already in order so there is no misunderstanding. The very first time I noticed I had an issue with the car it was running rough at times which popped the P0302 code. Since I had last bought coils and packs from FCP Euro, I bought new ones and did a lifetime return. After the next day I noticed the P0153 code pending. Since the car at the time was over 250,000 miles on the original O2 sensors, I replaced both banks Pre sensors with new Bosch and at a later date I did the post O2 sensors with new Bosch. I took it as so many miles maybe it is starting to loose its life expectance as I have read in the forum that they are technically good up to 100,000 miles which I already pretty much double that. Not 100% sure if I buy that now.

So basically after the O2 sensors were replaced on and off again I mostly got the P0174 code either pending or stored and the P0153 either pending or stored. After the O2 sensors being replaced I bought a smoke machine off Amazon and smoke tested the car probably about three different times and could not find any vacuum leaks as reading up on the cause of P0153 code could be a possible vacuum leak. At this point I was coming close for inspection and needed to get the car to pass. I did have a few years back a P0174 code and after replacing my MASS Air flow sensor it cleared the issue at the time. So since I bought from FCP Euro, I did a return for a new one. Cleared the codes and passed inspection with no issue. I was wondering if it did the job so for about 2 months I had no pending or stored codes. I was like great it is fixed once and for all.

At the beginning of this month I started getting once again the P0153 code. Two weeks later my light came on and I said let me take the car to get it checked out as I have been busy with work and not finding enough time to sit and troubleshoot the issue correctly. That is when I took it to the shop. I explained everything the car would do and what parts I had already replaced on the car. They assumed at the time it is probably a vacuum leak. The following day they contacted me and said they could not either find a vacuum leak and recommended to replace again my O2 sensors at $1175. I was not 100% sure if it was was for all 4 or just the 2 sensors. I told them no thanks as I already once again told them I replaced them in the beginning. When I went the next day to pick the car up I spoke to actually the tech who worked on my car and he was not aware I had changed the O2 sensors as the guy on the phone just writes the cars up and didn't pass the info. The tech at the time thinking what issues I had and based on mileage then recommends I replace my fuel injectors. Didn't ask for a price as I was ok.

It was at this point I decided to get the OBD fusion app and do the downloads that hopefully somebody could read the logs and give me some guidance. Or hopefully fix the problem once and for all.

Sorry for the long post as I wanted to make it known what the car was doing and what I already replaced. This car is basically my daily driver to and from work and I had this car since new over 19 years now. I enjoy driving it as it is fun to drive. Especially a manual.


See less See more
21 - 29 of 29 Posts
Let's look at the first part of the test

"With a hot engine at idle, record the 4 fuel trims. If any are >8% then you likely have a vacuum leak."

Your trims are all around zero, so there is no evidence of a vacuum leak.

The second half of the test where you rev the engine is therefore not needed. It does show that bank 1 long terms go rich with the short terms cancelling them out. Bank 2 is the opposite. Suggest you review post #6 and do the fuel pressure test to make sure you don't have a leaking injector.
Hey guys, I finally got the chance to checking my fuel pressure as I had to find time reading and figuring out what fitting exactly I needed for the fuel rail. A lot of trial and error as a lot of the stuff online is not clear on what is needed for the E46 rail.

So I did a check of the pressure by just turning the ignition to prime the rail and got 45 PSI. Pretty much steady. When I started the car, I had a steady 50 PSI and sometimes fluctuating between 50 to 51 PSI. The only test I could not do is drive with the gauge hooked up as I could not get it to reach to the drivers side and be able to close the hood.

I would think that my fuel pump is good since 50 PSI is what recommended by BMW and what I read on line. The only think I am not 100% sure is if priming the rail 45 PSI is normal without running the engine.

What do you guys think it advise where should I go from here. Thanks
It's been a while since I've looked at your problem. So, had another look at your logs.

The bank 1 long terms fuel trims are always negative, where as the bank 2's are always positive. A negative fuel trim means that the DME is taking fuel away from a rich bank.

You have new Pre-cat O2's and a new MAF. The only item in the middle that will give a rich bank is the injectors. A leaking injector could be your problem.

There are two way to test for a leaking injector:
  • With a fuel pressure gauge on the fuel rail. Prime the fuel rail then turn the key off. You should not lose more than 10 PSI over 15 minute or so. If the pressure drops quickly, then the fuel is going somewhere. Either a leaking injector or leaking non return valve in the pump.
  • Remove the injectors and fuel rail. Install the injectors into the fuel rail (with retaining clips) and prime the fuel rail. The leaking injector is the one that drips.
One thing I noticed which I didn’t mention is my car is been sitting in the garage for almost a week that has not run. So when I went to set up to finally hook up the fuel pressure gauge, I first pulled the fuse for the pump and wanted to run the car so it could starve of fuel. But the car right away didn’t want to start. Didn’t know if sitting like that is normal. After I hooked everything up to the rail I put the fuse and primed the rail and right away got a reading of 45 and turned the car on which right away I got 50. Didn’t have any issue starting. Now the fact it sat for a week and first turn on the key with fuse out didn’t start is a sign of injector you might think? Or maybe pump? Or just normal if it sat for a week? Prime and start was no issue.
The bank 1 long terms fuel trims are always negative, where as the bank 2's are always positive.

You have new Pre-cat O2's
Check if you cross connected the pre-cat O2 sensors. That can lead to one bank lean and the other rich.
Or just normal if it sat for a week?
Just normal after a week of sitting. The fuel pressure will bleed away over several hours/days.
Check if you cross connected the pre-cat O2 sensors. That can lead to one bank lean and the other rich.
Bali this was brought up before post 14 and 15 and I clarified it on post 17.
  • Like
Reactions: 1
I finally got to take a look at the injectors. As I pulled the injectors out to check the for any leaking injector I noticed they don't look that clean. I did not do the leak check on the injectors due there condition so I pulled them off the rail. A lot of carbon build up on all of them but did notice the bank 2 injectors had more than bank 1. I attached pictures below to see. The first picture at far right in order is from cylinder 1 - 6. The tips on bank 2 seem to have more build up to me.

I was thinking about sending them out to be cleaned as a co worker of mine knows a place that could clean them but thought at over 271,000 miles and the way they look with a lot of rust on the body of the injectors I might as well get new ones. What do you guys think?


See less See more
Its Fixed

It has been awhile but just wanted to update the post what I finally went through to fix this issue.

As the last post I took the injectors out for cleaning which did not work out as expected. After getting them cleaned I installed them back in and had the same issue. Started with pending codes for P0174 and P0153 till the P0153 came back with the light on. I was also starting to get a random misfire on cylinder 3.

I then found a shop near me which the person used to work at a BMW dealership. Just so happened to be the dealership I originally bought the car. Great guy which he sat for about a half hour and listened to everything I did to the car. He even was amazed of everything I tried to fix it and even gave ideas what it might be. But not what the end fix was actually. I did first go to the shop when my codes were pending and finally made an appointment after the light came back on. I dropped it off and within 2 days he called me back and advised that both CATS were clogged. Everything was throwing the car off due to the clog causing back pressure in the cats.

After doing some thinking I decided to spend the money and fix the car which the car now drives night and day. The car is quite compared to before and has the power which I had not felt in a long time. Plus my gas milage has improved by a lot.

I know a lot of posts get posted with no resolution to an issue so I wanted to let the forum know in case a similar issue happens to somebody and I want to thank for the help from NZOOZ3 and Bali for looking into and giving advise on this issue.
See less See more
  • Like
Reactions: 2
21 - 29 of 29 Posts