plowery21

Got the check engine light. Took it in and was told the code was for "Mixture Control 2 - Too Lean". I was not provided the exact code. They smoke tested and cleared the code. Lights off and it runs fine..for now.

Can anyone throw out some input for how the fuel mixture can get too lean...ie the lack of oxygen? I recently had my valve cover replaced due to a crack..which was found after some mixture control codes... The link to that thread is here: https://5series.net/forums/e60-discu...-cover-139340/

I have a K&N air filter with about 15K on it. Even BMW didn't think there was any problems with the aftermarket air filter. I have removed the air filter and everything looks fine for a laymen. Is there a sensor that could be going bad for the mixture control? As always, thank you for any input.

plowery21

I need to revive this thread because I am having the same issues and hope that someone may have advice here. The check engine light has been on and off since December 2014. My CPO warranty is up in June and BMW still says that they can't find an issue. Its been in multiple times now with the same code each time. I removed the K&N a while back and went back to standard OEM to see if that would help. I let them have the car for 2 weeks and they couldn't get the light to come back on after reset..and it came on again today 2 days after I picked it up. There is no noticeable performance issues while light is on.

The service advisor mentioned that maybe its carbon build up. The car is at 70,000 miles. Is that possible this early in the cars life? Of course CPO doesn't cover carbon blasting..

It seems to me that they would be able to replace the sensor that produces this code, but maybe its deep in the engine.

Any insight would be appreciated. Im tempted to take it to an indy to diagnose.
Thanks

Booyaazaa

Hey hows it going. I forgot are you running a tune or are running stock? I know I would get the mixture code when I run too much E85 in my fuel. Usually it would go away after I put in a gallon or two of 91 to balance out the mix.

turboawd

i'm guessing that code may be triggered by the forward oxygen sensors. they control air-fuel ratio, while the rear oxygen sensors monitor if the catalytic converters are doing their job.
so either a finicky oxygen sensor, or maybe you have a vacuum leak??

plowery21

Thanks Booyaazaa. Completely stock, no tunes of performance mods. I run 93 full time with techron added once an oil change to keep the injectors clear.


Thanks turboawd. I wasn't sure exactly how the sensor array for the car is set up for the fuel mixture control. I would think BMW would just replace them as a last resort fix.. Every time I take it in they run a "smoke test" and it passes. They replaced a few vacuum hoses to be sure last month but the light came back on. Basically this all started with a cracked valve cover, which makes me think a sensor got damaged in the repair. I will call and discuss further with the SA at BMW.