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Ming Feng

Ming Feng 4/20/2010

2001 BMW 525i Base 6 Cyl 2.5L


My car's Engine Service light is on. The DTC code are P0171 and P0174. What is the problem? How to fix it?

In a few times , when I just started the engine then runing idle, the light was come on. I erased the light. After 2-3 weeks, then the light was come on again. Sometimes the Engine Service light turned off automatically. When I drove, I felt anything was normal.

2 Answers


HouseCallAuto 4/20/2010

Check the air intake tube for a vacuum leak, check any hose for a vacuum leak anywhere on the engine. It could also be a bad mass air flow sensor. Further, more specific tests requiring a full service scanner are needed to pinpoint the one cause.

Bob R.

Bob R. 4/22/2010

P0171 System too Lean, P0174 System too Lean. The comment by Hous CallAuto is correct. There either is excess air getting into the intake after the airflow meter which is between the airfilter and the intake manifold, or the meter itself is defective or fouled by dirt from not replacing the air filter often enough. Look for cracks in the air intake bellows or any vacuum hoses. You can also purchase a special cleaning fluid for the airflow sensor at a parts store before you replace it.


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