Should vary a lot more than that, if it was pulsing the injectors it should show like 15 volts then 5 then 14 then 7 or somewhere closer to 0. So looks like your problem is the computer is not telling the injectors to squirt. I'm not that familiar with the M7 system so need to look up a wiring diagram to make sure where the computer gets its signal from to pulse the injectors. This will be the next place to test.