[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.

Hot Idle 11-24.csv

Shared with Dropbox

www.dropbox.com

Highway Cruise 11-24.csv

Shared with Dropbox

www.dropbox.com

Cold Start 11-24.csv

Shared with Dropbox

www.dropbox.com

 

[NZ00Z3]

Looking at your logs now.

What fuel do you run in the car?

• Pure Gas
• E5
• E10

There is something odd going on and knowing the amount of ethanol in the fuel will help.

 

[bluetech]

I use regular gas. 93 octane I always use since taking ownership of the car.

 

[NZ00Z3]

Sorry, I'm not in the USA so don't know the composition of the different fuels. I'll guess that it's E10.

 

[bluetech]

Sorry, I'm not in the USA so don't know the composition of the different fuels. I'll guess that it's E10.

Yes it is E10. Didn’t understand exactly what you meant.

 

[NZ00Z3]

Firstly, thank you for the excellent logs. Got them spot on first time out. Well done.

Here is my analysis file: 20221125 2004 330Ci Lean problems- Bluetech.xlsx

You might have multiple faults.

• A leaking bank 1 injector.
• A bank 2 exhaust leak before the pre-cat O2 or a loose pre-cat O2.
• A solf failing fuel pump or blocked fuel filter.

We'll start with Bank 1

Cold Start

• B1 Total fuel trim starts around -4% (rich). This is the last stored long term fuel trim. Running on E10, I would expect to see is around 5% (lean).
• Engine goes into closed loop control at around 50 seconds and both fuel trims follow a normal cold start trend B1 is slightly richer all the way through.
• Pre-cat O2 heating cycle is 0 to around 50 seconds. B2 follows the heating cycle perfectly. The SAP is dumping large amount of extra air into the exhaust making the exhaust very lean. B2 O2 sensor shows this. Now the B1 sensor is showing a rich mixture during this time. Either it's broken (but it's a new sensor) or the mixture is truly rich. Where would a 1 bank extra fuel supply come from? The only issues I can think of is a leaking B1 injector or a blocked Cat. It's really hard to get the E46 running rich. Either a leaking injector, blocked cat or a faulty sensor. The only Bank 1 specific sensor is the Pre-Cat O2 sensor. But it's a new O2 sensor.

Highway Cruise

• B1 Total fuel trims are cycling around -1% rich. In the days of pure Gas, this would be normal. But on E10 that should be cycling around 5% lean. B1 is still running rich.
• Pre-cat O2's. B1 O2 is showing sensible values.
• Post-Cat O2's. There is nothing to indicate a blocked Cat on either bank.

Hot Idle

• B1 total fuel trims are again rich, cycling around -2% rich
• Everything else has sensible values.

Bank 2

Cold Start

• Nothing unusual shows up in the cold start logs.

Highway Cruise

• The B2 total fuel trims are cycling around 10%. This is on the boundary for the P0174 code and why this code keeps coming up.
• All other charts show nothing unusual.

Hot Idle

• The B2 total fuel trims are all good, cycling around 2% lean.
• The noticeable thing between the cruise and hot idle logs is that the total fuel trims are worse at cruise than at idle. This is indicative of a soft failing fuel pump or a block fuel filter where it can't keep the fuel pressure/volume up to spec at cruise. Both the B1 and B2 fuel trims follow this trend.

Suggested next steps
Get a fuel pressure tester. One that fits the schrader valve on the fuel rail. Range is 51 PSI +/- 3 PSI

Check fuel pressure

• Key in position 2 with engine off.
• Engine running at hot idle
• Secure the gauge so you can see it and go for a drive to see if the pressure drops under load.
• Turn the key off and do a let down test for 20 minutes. It should not loose a significant amount of pressure, say 15 PSI. If it looses lots, and quickly, then you have a leaking injector.

Smoke test the exhaust to see if there are any exhaust leaks before the pre-cat O2's

Check that the pre-cat O2's are not loose.

Time Invested
It's taken 2 3/4 hours to spread sheet your logs and write up this post. I work for free, but it shows the level of work involved in looking at a set of logs. These one have been fun, they are not your normal issues.

 

[bluetech]

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.

 

[NZ00Z3]

Well, it looks like you have covered off all the normal repairs. I'll think some more.

One more item that will make one bank rich and the other lean is if the pre-cat O2's have been swapped. e.g. B1 plugged into B2's connector.

Can be checked by unplugging B1 while watching live data to confirm that B1 has stopped working.

 

[Landlorder]

Get ista software stop using p codes.

 

[bluetech]

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.

 

[NZ00Z3]

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.

You are correct. The B1 sensor lead should not be able to reach the forward most connector. It appears to be the connectors that people swap.

The easy way to check, is to look at the O2 sensor live data. Unplug one and see if that is the sensor that stops working.

Another common issue, is that people do not clip the sensor leads back into the correct retainers. The leads flop about and melt on the hot headers.

 

[Bali]

Easiest way to check for cross connected pre-cat O2 sensors is to disconnect one then look at voltages of both using OBD Fusion (or other scanner). The disconnected one will have 0V.

 

[bluetech]

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.

 

[Bali]

the O2 sensor closes to the front of the engine which should be bank 2 sensor 1

Nope. The front O2 sensor is bank 1 (for cylinders 1-3), not bank 2.

 

[NZ00Z3]

Nope. The front O2 sensor is bank 1 (for cylinders 1-3), not bank 2.

This is always a good discussion point.

It depends on the engine wiring configuration/car model.

• If the pre-Cat O2 connectors are mounted on the side of the engine, just above the exhaust heat shields, then the front connector is for bank 1
• If the pre-cat O2 connectors are mounted under the engine top beauty cover, then the front connector is bank 2

 

[NZ00Z3]

Just curious does anybody have an idea which direction this issue might be going since the O2 sensor theory is ruled out?

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.

 

[bluetech]

Nope. The front O2 sensor is bank 1 (for cylinders 1-3), not bank 2.

Just to clarify it is the connector in the circle of the pic.

 

[bluetech]

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.

 

[NZ00Z3]

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.

 

[bluetech]

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