I am looking for suggestions on how to troubleshoot for a no fuel pump prime pulse issue. Up until now, the system has functioned flawlessly for nearly 10 years.

Recently I started experiencing an intermittent engine starting issue. At initial engine startup when the ignition switch was turned on, I would periodically not get a fuel pump prime pulse. The problem has now progressed to no prime pulse. I checked all of the hardware such as FP relay, wiring and the ECM as I have a known good spare. In doing this I also verified that the ECM is not producing the prime pulse signal.

The engine is a Chevy MPFI V6 being controlled by a 1227727 ECM, $A1. I suspect VATS in the program may in some way be contributing to the issue although the ECM does not have any provisions for VATS. The $A1 program does have fault codes for VATS, but they are all unchecked and therefore should be turned off.

Any thoughts on how to remedy the problem?