I just bought a 2001 duramax with 1.5 million kms on the body and drive train. The engine has been replace and now has 200,000km on it, had 1.3 million kms on the first engine!! The problem is that the oil pressure gauge stays maxed out. I was told it was the gauge cluster, so i replaced it and it is still the same.( had to replace any ways odometer read 999,999kms) So i went to napa and bought a sending unit, but it is not the same as the one on my truck. The one i bought has 1 wire and the one on the truck has 3 wire. So im wondering is the engine in my truck newer?? If so how do i get the oil pressure gauge to work??