01 325i CEL when Air Pump is running

[Schwartzy]

I have a 2001 325i and it will idle rough and throw the CEL (P0174) if I start it up and let it idle while the air pump is running. If I hold the rpm's at 1500 until the pump shuts off it will idle perfectly and not throw a CEL.

Any ideas/suggestions would be appreciated.

[randy72877]

Lean codes usually indicate a vacuum leak. Do a smoke test first. Lots of possibilities. Lots of info here about it.

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[MarcoZandrini]

The problem is likely in the secondary air pump system. A smoke test may not find the vacuum leak if the SAP isn’t running.

[johnjmurray]

Check the big SAP hose for cracks. Mine was split underneath, not obvious. Also double-check the small vacuum hose coming from the valve on the motor. The rubber really cooks in that location.

[Schwartzy]

Thanks all, I guess it's time for a duck hunt.....LOL