I have a 2001 Tahoe 5.3L 2wd. I have a persistent battery drain. Battery will be dead after 24-36 hrs. I have noted that with ignition off, 30 sec. after doors are either shut or locked, courtesy lights go out and fuel and temp gauges come on and read fuel level and engine temp. Gauges will continue to read levels until doors are either unlocked or opened, when the return to zero. Could this be a BCM or RAP relay issue. Any input would be greatly appreciated.