I've read a few threads where MINI dealerships have told folks that their SES light was caused due to a poor sealing or loose fuel caps.

If that is so, why can I start my MCS with the fuel cap off and get no SES? I also removed the cap while idling, and got no such warning (SES light activation)...

It's a fairly long story as to why I'm doing this, but I just wanted to make sure that my SES was still operable (or working properly) with a piggyback ECU in place. I wanted the easiest way to trigger an SES, and the fuel cap came to mind, but it didn't do so...

I did pop-off the wires to the the TB, and that got an SES for sure! I remain curious about the fuel cap though. Anyone willing to try this? If it does come on, don't worry. Re-affix the cap, and after several restarts, all will be fine. I just turned-off my SES from the TB experiment just that way...

Thanks guys!

 

I've done this test myself, but it seems to only work one way for me. When you're close to empty, go get some gas and then leave the fuel cap off when you leave the gas station. The large difference in pressure from empty to full seems to trigger the light after a mile or so, but my SES light does not illuminate. There is another light "Check Filler Cap" that illuminates on my dash. Try it out. Once you reinstall the cap, the light will go out.

 

Heck, that makes a lot of sense! Thank you, and I will try it. Fun stuff!