just replaced thermostat in my 2002 ram 1500 slt 4x4 with the 5.9 magnum about 6 or 7 months ago and and it is already failing. Will throw a code that says thermostat inactive. Particularly when its cool out. What would make it fail already? Also getting a pretty heavy vibration between about 45 to 65 mph and only when accelerating and it is the worst around 50mph what would cause that? Tires are aligned and balanced by the way. Appreciate any help i can get here.

 

Did you replace the thermostat with a Failsafe unit? Those tend to fail pretty quick. I've had them fail in anywhere from a few days to a couple of weeks.

 

I dont honestly know. Thats entirely possible. Definitely not using one this time.