I am getting trouble code is P0521....Engine Oil Pressure Sensor/Switch Range/Performance. The Gauge light was coming on and the Oil pressure gauge was going down to zero and then back up to 40, and the light would go off. I replaced the Oil Pressure Switch (which is on back side of engine behind throttle body on my 2005 5.3l V8). Now the Check Engine Light is on and the trouble code P0521....Engine Oil Pressure Sensor/Switch Range/Performance is still coming up on the scanner. I have tried to erase codes but check engine light comes back on and I get same P0521 code. Can any one help out with this fix???