I have a 2003 Blazer LS, 4x4 4 door

My fuel gauge quit working, it is stuck on E with the low fuel light on. I unplugged the connector at the pump, and with the key on i have 5 volts on the purple wire and black/white is a good ground. Does this seem right? Unplugging the sender does nothing to the needle. I've heard the gauge itself can go bad, is there any way to test this? Where should i start? Is the pcm supposed to detect voltage coming from the purple wire to determine gauge position?