PO174 Only Code

[rautis2]

Hi I have a 2004 X3 and keep getting this code alone. Anyone have any ideas on what it might be?

[MIKYZZ4]

Indicates lean fuel conditions-Bank2.
Since only affecting a single bank,
doesn't appear to be an intake leak.

I would swap pre-cat O2 sensors across banks, as a test.
If code transfers to bank1(P0171), then we have found our culprit.

Don't mix up sensors or harness connections, label and mark them!

[rautis2]

It did not work. We have replaced the oil separator hose due to it was shot. We have also cleaned both mass air flow and IAC valve. Performed smoke test finding the busted oil hose. Still have same code and and are almost at our wits end. Not sure what else to do

[MIKYZZ4]

BMW engines do not appreciate the value of a piecemeal approach to system repairs.
In the case of that deteriorated oil hose, if a single hose was found in that condition,
what do you suspect is the condition of the remaining components of the PCV system?
Replace the system as a kit, here:https://www.fcpeuro.com/products/bmw...11617501566kt5
Notice the amount of parts/seals that prevent vacuum leaks to the system, as a simple crack in any one of those components,
can and will lead to unmetered air intrusion-causing a lean code.

Was a test performed using a pro smoke machine?

After each attempt at repair,
do you clear codes followed by a short drive cycle?

[bdiefAZ]

You likely have a vacuum leak somewhere on the engine, check the intake boots, they are the largest culprits of leaks. Other sources are CCV system, vacuum hoses/caps on the manifold, throttle body gasket, and manifold gaskets.

What is the mileage on your X 3?

[bdiefAZ]

You likely have a vacuum leak somewhere on the engine, check the intake boots, they are the largest culprits of leaks. Other sources are CCV system, vacuum hoses/caps on the manifold, throttle body gasket, and manifold gaskets.

What is the mileage on your X 3?