Check engine light

Greetings,

I have a 2001 740i with ~ 70k miles. It has been a great car since I bought it 4 years ago.

An year ago or so I noticed that my check engine light would turn on when the tank was full, turns off when it reached 3/4 and turns on again when it reaches 1/4. Almost like clock work.

I took it to a good mechanic, he read the code and mentioned something about the air mass indicator. I did some reading about it and could not find any correlation between it and the fact that the check engine light seems synchronized with gas level.

So, any ideas?

Thanks,

Mayeb your fuel pump is going south...can't keep a good enough pressure outside of 3/4 and 1/4 full...

What was the diagnostic code? Did the indy happen to give that to you? Were there any other codes pulled?

Could be as simple as a faulty fuel cap, the recirculation system is fairly touchy on the E32 at least. This will trigger the CE light. Have you noticed any other issues? A new fuel cap worked for me when I had similar symptoms. Worth a look.

I have a 1997 740IL with 150K miles. My Service Engine Soon light came on. I read the code at my local Autozone store. The codes were P0420, P0133 and P07xx. I replaced my pre-cats O2 sensors, fuel filter and cleaned my throttle body with a throttle body cleaned obtained at Autozone. 50 miles after, the Service Engine Soon light went off.