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2004 330ci
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64 Posts
Discussion Starter · #1 ·
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.
 

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2004 330ci
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64 Posts
Discussion Starter · #7 ·
NZ00Z3 thank you for taking the time analyzing my trims and responding to my post. I will start by purchasing a gauge to read my fuel PSI and report back. Just so you know the fuel pump was replaced about 4 years ago and my filter just prior to the pandemic so I would say 2 1/2 years ago. Also I never did smoke test my exhaust side but the tech at the shop said he did it and he couldn't find anything leaking on that end.
 

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2004 330ci
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64 Posts
Discussion Starter · #10 ·
A little update. Unfortunately the fuel PSI tester I bought off Amazon is not compatible to BMW since the fittings it comes with do not fit. After I received it and opened the package I read only for Chrysler and GMC automobiles. I am just going to get the harbor freight brand and just use that. Sucked since I took everything apart to try and check my PSI. More to come.

One thing if somebody could look at there car and tell me which plug for the PRE O2 sensor is bank 1 and bank 2. On my car the Bank 1 sensor goes to the most AFT connector towards firewall and Bank 2 goes to the most FWD connector. I cant see if I swapped them wrong since according to FCP site were I bought them it says the same P/N for Bank 1 and Bank 2 so they are the same exact length. So Bank 1 O2 sensor should not reach the most FWD connector . Only the most rear connector is going to Bank 1 on my car. Remember I have an 04 which has the 5 PIN plug wide band O2 sensor. Thanks.
 

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2004 330ci
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Discussion Starter · #13 ·
Ok I am back. I finally found time to check if my O2 sensors are crossed and the result is they are not. I disconnected the O2 sensor closes to the front of the engine which should be bank 2 sensor 1 and it was connected correctly.

The voltage reading doesn't go to a complete zero reading but just stops changing numbers. Once I connected it again the voltage numbers start changing again. I also got a pending code P0050 which is O2 sensor heater control circuit bank 2 sensor 1. I did not try the fuel pressure reading as I did get a rental fuel pressure kit from autozone which again did not have the proper adapter to connect on the fuel rail. I will try and make it to harbor freight possibly and get a fuel pressure kit but might I have to wait till after the holidays.

Just curious does anybody have an idea which direction this issue might be going since the O2 sensor theory is ruled out? Could it be still the fuel injectors? Or the fuel pump that my pump is soft failing?

Oh also from the last time updated I did clear all the codes and then I started getting just P0174 lean bank 2 pending but not P0153 at the time. Also noticed right before I started the O2 sensor test I scanned and had zero codes at the time. No stored or pending codes. The car was a cold start as an FYI if that means anything.

Again thanks for the help.
 

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2004 330ci
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64 Posts
Discussion Starter · #18 ·
It could be a bad MAF. Best checked with a Rev-Rise Log.

Rev Rise.

This test is for checking your Mass Air Flow Meter (MAF). Hot engine and Cat’s, stationary car. The test is best done just after a drive.

Slowly raise the Rev's of the engine up from idle to 3,000 rpm. I mean slowly. It should take you 3-4 minutes to do this test. It takes some skill to do this test due to the lightly loaded engine. A little throttle change results in a large rev change. Don’t run up and down the rev range getting used to the control. If you stuff up the first part of the test getting used to controlling the small rev changes, then redo the test.

Post the log as per- before and I'll have a look.
One thing is if you remember reading on my first post I did just change my mass airflow sensor. I was getting those codes randomly before and after the change. But after I did the change it took almost 2 months before the pending code started popping up again and almost a month later the check engine light popped on as stored code. I also got the mass air flow sensor from FCP and was OE. Continental VDO brand. No eBay cheap stuff. Also this is technically my second mass airflow sensor since a few years ago I kept getting a P0174 lean code. After changing the mass airflow sensor it took a few years before I was getting at least the P0174 code.
 

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2004 330ci
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64 Posts
Discussion Starter · #20 ·
Mixture codes can be broken down into:
  • Vacuum leaks causing lean codes. Most common
  • Failing Pre-Cat O2 sensors (rich or lean codes)
  • Failing MAF (rich or lean codes)
  • Exhaust leak before the pre-cat O2 sensor. Gasket or SAP problem. Causes lean codes
  • Loose Pre-Cat O2 sensor, causes lean codes.
  • Swapped pre-cat O2 connections. One bank goes lean and the other rich.
  • Blocked Cat's. Can be lean at hot idle but rich under load.
  • Performance coding of the DME causing rich or lean codes.
You've covered most of the bases with new parts already.

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

Rev the engine to 3,000 rpm for 30 seconds and watch the short term fuel trims. If they drop significantly, might even go negative, then it is confirmed that you have a vacuum leak to find.
NZ00Z3 I did the mixture test you mentioned above and uploaded it. Could you please take a look and tell me what you think?CSVLog_20221219_163528.csv
 
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