2003 GMC SIERRA 1500 HD Engine Problems

I AM AN ASE MASTER TECHNICIAN, I OWN AN AUTO/TRUCK REPAIR FACILITY. WE ARE A STATE OF OREGON AUTHORIZED DEQ REPAIR FACILITY, STATE OF OREGON DAS FLEET REPAIR FACILITY, US ARMY BASE VEHICLE REPAIR SHOP AND MORE. DRIVING MY TRUCK TO TACOMA WASHINGTON. I WAS TOWING A VEHICLE ON IN THE RIGHT SLOW LANE, AND "REDUCED ENGINE POWER" LIGHT CAME ON. ENGINE VIBRATED AND RUNS ON 1/2 CYLINDERS. CANNOT BRAKE OR STEER, TOTAL LACK OF POWER. SEMI-TRUCK NEARLY REAR ENDS ME AS I CANNOT GO OVER 10 MPH. NO THROTTLE RESPONSE, PERIOD. I WAS IN ROAD CONSTRUCTION ZONE AND EVERYONE WAS SLAMMING ON THEIR BRAKES TO AVOID PILE-UP AS I HAD NO SHOULDER TO PULL OVER TO. A MILE OR SO LATER I PULLED OVER, AND SHUT OFF TRUCK. RESTARTED FEW MINUTES LATER AND CEL WAS ON, BUT REDUCED ENGINE POWER LIGHTS OUT. I CONTINUED MY DRIVE, BUT NOW CAUTIOUSLY....

I EXPERIENCE AN INTERMITTENT PROBLEM WITH MY TRUCK THAT FLASHES AN ERROR CODE "REDUCED ENGINE POWER". THIS IS TIED TO ERROR CODE P1516. USUALLY THIS PROBLEM OCCURS IN COLDER PARTS OF THE YEAR, AND ON A COLD SOAKED ENGINE, BUT IT HAS HAPPENED OTHER TIMES AS WELL. AS SOON AS THE ERROR OCCURS THE THROTTLE SHUTS AND LEAVES THE VEHICLE WITH ONLY INERTIA TO ATTEMPT TO GET OFF THE ROAD. THIS HAS HAPPENED TO ME ON THE INTERSTATE, AND THOUGH I HAVE NOT HAD AN ACCIDENT YET, I DO CONSIDER IT DANGEROUS. I HAVE TAKEN THE VEHICLE TO MY LOCAL DEALER AND INDEPENDENT MECHANICS, AND THEY HAVE BEEN UNABLE TO RESOLVE THE PROBLEM. THIS SEEMS TO BE A WIDESPREAD PROBLEM WITHOUT A SOLUTION. *TR