3.0 P0172 and P0175 codes

[caposto]

I bought my 2002 X5 3.0 a year and a half ago. I was getting these two codes every now and then but now its more regular and I've got a smog coming up. They are "Bank 1 too rich" and "Bank 2 too rich." The only thing I could find was it could be a dirty AFM so I cleaned it and the contacts but no change. There also seems to be no rhyme or reason to when the codes are tripped (hot, cold, accelerating, idling, etc.) P0172 trips first and then shortly after I get P0175.

The service is up to date on it so was hoping you all could point me to possible causes. Any help would be much appreciated. Thanks!

[caposto]

After a little more searching just now, I seem to have found a thread with the problem solved here: http://www.xoutpost.com/bmw-sav-foru...0175-dtcs.html

I can only assume the intake boot leak is causing a lean condition and the ECU is over-compensating with fuel, as the cracks let un-metered air through, and then those cracks 'seal' up a little as the engine vibrates and moves and the ECU can't adjust back quite quick enough. Just a theory, but I will be checking my intake boot and other hoses right away!

[Joshdub]

I had the same thing recently. Chances are the codes are wrong and it's a really running lean. You probably have a vacuum leak. Just start replacing old hoses.

[X53Jay4.8is]

Originally Posted by caposto

After a little more searching just now, I seem to have found a thread with the problem solved here: http://www.xoutpost.com/bmw-sav-foru...0175-dtcs.html

I can only assume the intake boot leak is causing a lean condition and the ECU is over-compensating with fuel, as the cracks let un-metered air through, and then those cracks 'seal' up a little as the engine vibrates and moves and the ECU can't adjust back quite quick enough. Just a theory, but I will be checking my intake boot and other hoses right away!

Have the engine smoke to determine where the leak is that causing the lean code.

[caposto]

Thanks for your thoughts. I will investigate further now that I have some direction on what to look for and post my findings and outcomes in hopes of helping others.

[upallnight]

Why is it that when people post their trouble codes on this forum, other people will tell them that they are misinterpreting the code.

P0172 and P0175 are both Rich Codes. A rich condition is when you have too much gas in the mixture or too little air in the mixture.

Too much gas could be due to the fuel pump pressure is too high. You can verify this with a fuel pressure gauge at the rail. It can also be due to a leaky injector(s). You can also verify this at the fuel rail with a fuel pressure gauge.

Too little air could be due to a dirty air filter, bad maf or a bad iac valve. When did you last replace the air filter? If you have a scanner that can provide real time data, what is the airflow rate that the MAF is sending to the DME (G/S). When did you last check, service the IAC valve?

Fuel trim data will verify if you have a rich or lean condition. If the trim data is negative that mean the engine is running rich. Freeze frame data will tell you as to what the engine was doing when the code(s) was set. Is the engine thermostat open so that the engine doesn't warm up so the DME is adding fuel to a cold engine.

Only right way to work on these computer controlled engines is with a scanner that allows you to view real time data.

[crystalworks]

^I was thinking fuel system as well. Injector(s), regulator, etc. Not reaching operating temp would also cause a rich condition as upallnight mentioned.

Though, the M54 is widely known to suffer from vacuum leaks as well, just like all the BMW straight 6's. I would guess it would need to be a largish leak to cause the ECM to compensate enough to throw a rich code. Usually vacuum leaks are misfire and lean codes.

Also a good idea to see if you can get live data from the X. Will help your diagnosis. I think he's said he uses Torque, which I have used in the past as well. You need to see what the fuel trims are doing as he mentioned.

[upallnight]

Originally Posted by crystalworks

^I was thinking fuel system as well. Injector(s), regulator, etc. Not reaching operating temp would also cause a rich condition as upallnight mentioned.

Though, the M54 is widely known to suffer from vacuum leaks as well, just like all the BMW straight 6's. I would guess it would need to be a largish leak to cause the ECM to compensate enough to throw a rich code. Usually vacuum leaks are misfire and lean codes.

Also a good idea to see if you can get live data from the X. Will help your diagnosis. I think he's said he uses Torque, which I have used in the past as well. You need to see what the fuel trims are doing as he mentioned.

Torque Pro, I believe in giving back to the people that devote their time and effort to develop an App. My philosophy is that if you like the App you should buy the App.

[crystalworks]

Originally Posted by upallnight

Torque Pro, I believe in giving back to the people that devote their time and effort to develop an App. My philosophy is that if you like the App you should buy the App.

Agreed. It's not an expensive app if memory serves. <$50

[upallnight]

Originally Posted by crystalworks

Agreed. It's not an expensive app if memory serves. <$50

When I bought the app it was $4.99.