oil pressure stays @80lpsi..where is the sensor located?

Most likely it is the oil pressure sensor that is bad. It should be located directly above the oil filter or possibly on the back of the engine block between the heads and behind the intake manifold.

FUZZYWAHLERS@GMAIL.COM

Oil pressure is on the back of the block between the cylinder heads. Bad oil pressure readings are most always caused by either a bad sensor or a bad oil pressure gauge inside the gauge cluster which is very common on the 03-06 Silverados. Each gauge has a motor that controls it's needle movement and when the motor goes out the gauge will either stick, jump around or die all together. If you'd like to learn more about the problem and how to get it fixed please visit our site at www.drspeedometer.com Thanks, Fred Dr.Speedometer