Originally Posted by Henn28

+1. Some e53s don’t have FPRs (mine is a 2002 and has the smaller filter without one), but most have a larger filter with the FPR sitting on the output end. I believe it can be bought separately.

Low batteries can cause all sorts of seemingly unrelated issues.

Make sure the car goes to sleep…16 min is advertised time for all systems to power down. Bridge the negative at the battery, or just upstream where it goes to the chassis by the fuseable link block behind the left rear seat. Best case is you secure the meter leads, position the meter where you can read it thru a window and shut and lock the car. Hack your watch and wait. The amps may drop off in a couple increments as systems go to sleep, but at 16-ish min you should see the meter drop to .05. Mine fluctuated between .04 and .06. If it doesn’t then you need to pull a likely culprit fuse and do the whole thing again…and rinse/repeat as many times as necessary until you find the draw.