LS4 common problem the last chance filter under oil pressure sensor should always be replaced when replacing switch. Oil pressure switch GM #12616646 or AcDelco #D1846A the last chance filter is GM#12585328 they list it as valve lifter filter. Both can be found at online (Rockauto-E-Bay). Ok after watching you tube video's don't do what they do. First remove engine cover, unplug switch, use socket loosen up not all the way, one hand under one finger on top finish unscrewing and remove, now make sure sealing area is clean, next look down in the filter has 2 ears on it use a good pair of niddle nose pliers grab one ear and pull up and out. Now lube new filter o-ring with oil use pliers to insert then snap in place, install new oil switch. Just did one today total time 12 minutes. Just a note using synthetic oil 5W30 oil you will find this filter usually clean.
