Our 2007 GMC Yukon XL 5.3L 2WD is chiming the alarm and sending a message across the dash to "shut engine off, oil pressure low". It ONLY does this when the vehicle stops ( red lights or stop signs). My husband has changed the oil pump, oil filter, cleaned the oil pan and the screens, and changed the oil sending unit.....and it still does it. you can hold the brake and give it some gas to get the RPM's up to 500 and it stops. While the vehicle is running the alarm isn't sounding, but the oil pressure fluctuates between 30 and 60. When the oil pressure falls, the car will not respond to acceleration, after you accelerate, the vehicle will pause and then kick in and will speed up. Any ideas on what can be done next?