Check Engine Light.

[car34]

2000 740il. The check engine light comes on. With the scanner I have it says it is Genaric Code 171 System to lean on bank 1. I did replace both of the Ox sensors before the cats. Going to change the rears next week. After thinking about I guess I should have replace the two on bank 1 Frist. Has any one else had this same problem? What else would cause just one side to be lean? No Vacum Leaks that I can Find.

[bryan1970]

while it could be faulty O2 sensors sometimes the intake manifold gaskets can leak a very small amount and casue the fault. and be hard to detect aswell. how many miles are on the car? another thing that can casue a lean mixture and is also common on the V8's is the backing plate on the intake manifold. it is kinda like a sophisticated PCV valve. however they are usually quite noticable if they fail. for one there should be lean faults for both banks, the engine will smoke blue smoke( oil being burned), and most of the time thay make noises. i have herd of the noises being described as a sound similar to a turkey