Probe the wiring with a dvm, where do you have power in the circuit. Do you have power before the relay? Could be many causes from ignition switch failing, fuse links, short in wiring, bad pump or even the ecu..
Might be the ECM. Just had to get mine rebuilt. I had the issue where I could run the jumper cable to cause the fuel pump to run but no luck when just using the key. The ECM rebuild did the trick. Try using the jumper trick to see if you're getting a signal back there. Also the check the inertia switch (trunk) first.