THE REAR POWER DOOR LOCK ACTUATORS HAVE FAILED. THE REAR PASSENGER DOOR LOCK FAILED FIRST, THEN A FEW THOUSAND MILES LATER THE DRIVER SIDE ACTUATOR FAILED. THE PROBLEM IS INTERMITTENT BUT WITH A 90%+ OCCURRENCE OF FAILURE. ONE OR BOTH WILL FAIL FOR WEEKS AT A TIME, BUT MAY OCCASIONALLY SURPRISE YOU AND WORK ONCE OR TWICE. THE FAILURE IS IN BOTH THE LOCK AND UNLOCK MODES. THE FAILURE IS UNRELATED TO USING KEYLESS ENTRY OR THE MANUAL SWITCH OR HAVING CHILD SAFETY LOCKS ON OR OFF. IT IS VIRTUALLY IMPOSSIBLE TO REACH THE REAR DOOR TOP MANUAL LATCH POST FROM THE FRONT SEAT. ON ONE OCCASION I WAS TRYING TO MANUALLY UNLOCK THE REAR PASSENGER SIDE DOOR FROM THE FRONT SEAT. MY HEAD/NECK BECAME TRAPPED BETWEEN THE SIDE OF THE FRONT PASSENGER SEAT AND THE DOOR PILLAR. I WAS UNABLE TO REMOVE MY NECK UNTIL I WAS ABLE TO REACH THE SEAT ADJUSTING MECHANISM AND MOVE THE SEAT FORWARD. IN THE PROCESS OF THAT I AGGRAVATED A CHRONIC BACK CONDITION PULLING A MUSCLE IN MY BACK. AN INTERNET SEARCH OR DISCUSSION WITH REPAIR SHOPS WILL QUICKLY REVEAL THAT THIS IS A WIDESPREAD ISSUE FOR MANY 2008-2009 CHEVROLET IMPALA, TAHOE, MALIBU AND SILVERADO OWNERS. DUE TO THE APPROXIMATE $365 PER DOOR REPAIR COST, THE DEFECTIVE LATCHES ARE NOT BEING REPLACED BY MANY OWNERS. CHEVROLET IS WELL AWARE OF THE PROBLEM AND OFFERS NO REPAIR ASSISTANCE. IN A CRASH SITUATION THE CRASH COMPUTER SEQUENCE CANNOT BE RELIED ON ACTUATE THE DEFECTIVE LOCK ACTUATORS. THE POSITION OF THE MANUAL LOCK