Error code 227/228 and 251

[Krystanimyth]

Hello All:

My 2000 M Roadster just had a trip to the shop to get the starter replaced. (~4 miles from home)
On the way home I got a full tank of Super grade gas. (Less than 1 mile from home)
Somewhere between picking up the car, getting gas, and getting home the "Check Engine" light came alive. I noticed it on the way home from the gas station, but that only means I noticed it then. It may have been on since the mechanic shop.

Error Code 227/228 are for "Mixture deviation" in cylinder 1-3 (227) and 4-6 (228).
Error code 251 is "Tank leak detected, Minor leak"

My first thought was maybe I didn't put the gas cap on correctly (before diagnostics, I have had this happen before on other cars). Not the case. I brought it back to the mechanic and they swear it is just a coincidence, and the starter has nothing to do with this set of errors.

I work in IT, and there is a long-held adage: if you change something, and things break, it is 99% sure it is due to your change. However, I also got a tank of gas. It is possible it is bad gas. Nothing explains the 251 Tank leak (minor or not), and there is no gas leaking anywhere I can see, and no gas smell coming from the engine.

I need so expert advice - before I decide to bring the car for a very expensive trip to the (not so) local BMW dealer. What do the experts here think this might be? Bad gas? Mechanic did something wrong? Completely a coincidence and I better get to the BMW Dealer?

Thanks!

 

[Sajk]

The 227 and 228 should be unrelated to the other things. It would be best to use something like inpa to see if the deviation is rich or lean. As an afterthought check that the pre cat lambda sensors are plugged in the right way. I have seen the front cable plugged into the rear bank and visa a versa. This quickly leads the the fault you describe as the dme tries to adjust the mixture using the wrong information. The was not on a bmw and I don't know if the cables are long enough but if for some reason they were disconnected when the starter was changed it could be.

 

[Pingu]

@Sajk makes a good point. They probably have swapped the lambda sensor plugs, as they are beside the gearbox and would probably have been unclipped to provide more access.

One will now be tight and the other will be loose, as they are slightly different lengths, but have the same connectors.