I had SES light turned on 2005 4.4i immediately after I performed an intermittent oil change. Engine oil level I checked with my dip stick was low after 8.5 quarts of oil so I put one more quart but it didn't fix the problem. I took my X5 to the dealer and my service adviser told me SES is only to do with exhaust system. After the technician checked the error code, my adviser asked if I have been very low on gas and I said "never."

Still they concluded that at certain point my gas was so low it messed up engine firing order. They had to reset it and it was good to go.

The interesting fact is during this period I was getting better gas mileage like +2MPG.