first my vehicle is an 08 yukon xl denali 6.2. I noticed over the winter oil pressure was low and shut off engine came on. once it warmed up pressure was low but the turn engine light off never came on. Now, if I dont get in and start driving the shut engine off comes on. when driving pressure is under 40 even at highway speeds it is below 40. and when I stop at a light it drops to almost 0 but shut engine doesnt turn on. I am wondering the chances if the melling pump is bad, or if it is just that stupid pick up tube o-ring. but would hate to take it down that far and change o-ring only to have same issue after. vehicle has 170k. lie I said when driving I have pressure, but when at a light after first starting it it says to shut if off unless I shift to neutral and give it a little gas. I am willing to do the oil pump but if consensus is it doesnt need swapped I will just do o-ring. also when I changed pressure switch there was no filter under the sensor. should I install one?