Point well made - vacuum leaks can trigger it (archive)

Thought it was also the case with my 94 740 but a careful mechanic diagnosed a couple of leaks + a failed thermostat -- car ran too cold .. both caused the Oxy sensors to try to overcompensate, trigger errors. The other symptoms - poor drive-ability, poor gas mileage also resembled O2 problems but when the leaks were fixed and operating temp brought back to normal the codes were cleared and haven't returned. BTW, the thermostat failed in the wierdest way -- the frame actually snapped and the thing locked up in the open position - thus the car always ran cold. I really didn't pay attention because the weather was warm. Mechanic said it wasn't unusual to see them go that way on the V-8's!

What a difference the repairs have made!

Lou

Hi,

I had this code and our local mechanic couldn't figure it out because, O2 sensor was okay, fuel injector was okay and spark plug was okay.
I took it to the BMW dealer and found out the intake manifold gasket leak.
So, make sure to do a thorough check up before you replace perfectly good O2 sensor or fuel systems.
Good luck.

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