WHAT I USAULLY DO IS CHECK FOR LEAKS,PULL THE EGR VALVE LOOK IN THE INTAKE FOR COOLANT,IF THATS OK THEN I CHECK FOR COOLANT FLOW AND FAN AIR FLOW IF THATS OK,THEN I ROADTEST AND LOOK FOR PIDS ECT AND EOT IF THATS OK THEN I DRIVE TRUCK TO GET IT TO VENT OUT COOLANT FROM THE DEGAS BOTTLE CAP THIS WAY OF DOING IT WORKS EVERY TIME