2003 GMC Yukon Denali Xl

VEHICLE POWERS DOWN WITHOUT ANY PATTERN, RHYME OR REASON. IT WILL DO IT AT 5 MPH, AND AT 55 MPH, WHEN DRIVEN A LOT, AND WHEN NOT. REDUCED ENGINE POWER LIGHT TURNS ON, VEHICLE SUDDENLY SLOWS TO 25 MPH MAX, STEERING BECOMES HARD, BRAKES TOO. THEN WILL TOTALLY SHUT OFF IMMEDIATELY. I HAVE REPLACED THE BATTERY, THROTTLE BODY ASSEMBLY AND WIRING HARNESS TWICE. FUSES, FUEL PUMP AND FILTERS, OIL, AND EVERYTHING ELSE AS RECOMMENDED. IT PUT ME IN THE DITCH. IT STRANDED ME IN THE CENTER OF A FREEWAY IN WINTER. WHEN IT SITS FOR A WHILE, IT RESETS, ONLY TO DO IT AGAIN. T/C LIGHT TURNS ON ALSO. I FOUND OUT THAT I CAN MANUALLY RESET THE REDUCED ENGINE POWER FOR A FEW MOMENTS (TO GET OUT OF THE CENTER OF THE ROAD) BY TURNING THE IGNITION SWITCH ON AND OFF VERY FAST. IT IS A EXTREME SAFETY HAZARD! I HAVEN'T DRIVEN IT IN MONTHS DUE TO ABSOLUTE FEAR FOR MY LIFE. WHEN ITS IN REDUCED ENGINE POWER MODE, I CAN'T GET IT TO GO ABOVE 25, AND GOING UP HILLS CAN'T GO ABOVE 5MPH. IF I AM PULLING A TRAILER, IT STARTS TO GO BACKWARDS. THIS THING IS GOING TO KILL SOMEONE! PLEASE HELP *TR

INTERMITTENTLY AT HWY AND SIDE ROAD SPEEDS, TRUCK WILL SHUT DOWN, CHECK ENGINE LIGHT COMES ON AND EXTREMELY ROUGH IDLE AND LOSS OF ENGINE POWER OCCURS. HAVE FOLLOWED ALL RECOMMENDED FIXES BUT PROBLEM PERSISTS. ENGINE CODE 1516, THROTTLE POSITION SENSOR OUT F RANGE +- .05 VOLTS. SCARY PROBLEM, AS THIS OCCURS WITHOUT WARNING AND CAUSES IMMEDIATE LOSS OF SPEED. MANY MANY COMPLAINTS POSTED ON THE INTERNET OF THIS SAME PROBLEM BUT NO GMC RECOMMENDED FIXES OR ASSISTANCE. REFUSE TO TAKE THIS TO A DEALER AND LET THEM POKE AROUND AT $95 / HOUR AND OR TO THROW PARTS AT TRUCK IN HOPES OF CORRECTING. GMC NEEDS TO ADDRESS THIS POTENTIALLY FATAL PROBLEM. *TR