The G540 can't prevent the ESS from generating the charge pump signal. Mach has to tell the ESS to generate the signal though. There is a slim chance your Mach3 profile is corrupt and doing goofy things like maybe telling the ESS to generate the charge pump signal at the wrong frequency. Your ribbon cable could have a very poor connection on that particular signal (unlikely) or it could be the G540 is just not working correctly. Unless you can test for the proper signal being delivered to the G540 you don't know where the fault lies. You could try creating a new Mach 3 profile from scratch I have seen that fix some really odd behavior before.