F4 FRS error

Greetings! I have an Advanti J26-XPI that is experiencing an intermittent F4 FRS errror. The Lid seal and port are have been cleaned, and the motor boot has been cleaned with a small amount of vacuum grease spread on the mating surfaces of the seals. On occasion the unit will run normally, while most often I am experiencing the F4 error. At all times the vacuum pump can be heard to be running when >5K RPM. Would appreciate any advice related to troubleshooting the F4 error, as well as general testing of the vacuum system. Is there a way to run the vacuum in a service mode while monitoring the vacuum level?