Suburban quits running while in drive

1999 suburban, K1500, 4WD, ~175,000 miles

Suburban has died three times in the last two weeks while in drive. Once on the interstate, once in a parking lot, and once on another street. The only common thread is the numerous clicking noises and the dash lights going off each time. The first time on the interstate I pumped the gas pedal and kept the car from dying. The other two times I was not as successful. This would indicate a fuel pump problem but I had the clicking noise issue a couple of months ago and it was a frayed battery cable.

The starter and alternator cable were piggybacked with the PCM cable to the side post of the postive side of the battery. The PCM cable was frayed at the battery end so I bought a top post connector and re-made the cable and attached to the top post, thereby not giving the PCM the voltage from the alternator but directly from the battery. Everything was working fine until two weeks ago. Voltage readings tonight, with vehicle running, show 13.8v at the side post (where the alternator cable is attached) and 12.8v at the PCM module.

My question is does the PCM (where the fuel pump relay is) have a threshold operating voltage that needs to be maintained for the vehicle to operate correctly or could it be the fuel pump again?

Factory fuel pump was replaced in 2005 at ~140,000 miles.

Thank you.