If it's not blinking now, limp your way to an Orielly's, Checker's or Kragen (whatever the local chain name is near you) Ask to borrow their OBD II reader to use in the parking lot. They may ask to hold your ID so you don't steal it, but it should be free. Local chains here will even print out the results for you in the hope you'll buy replacement parts from them.

It could be something major but last time it happened to me in my M5 I remember it being rather minor (cheap to fix) like a bad MAF or CPS.... I've gone through so many sensors on these cars it's hard to remember...

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Matt Atkins
'01 Titanium Silver X5 4.4
'01 Lemans Blue M5