I'm trying to diagnose my 2012 Jetta TDI with P048C and P0401 codes. Should the exhaust pressure valve move to a closed position on cold startup? I can hear it humming, but it doesn't move. I've taken it apart and lubricated it. It moves pretty easily, but with some resistance in my hand. I don't know if the motor doesn't have enough power to move it, or if the motor is defective.