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5 volt reference - 7 volt reference - elevated ground
most if not all systems on most if not all cars
do not use the system voltage for power supply s to the critical sensors whose precise input is needed to control things
there is a separate regulated 5 volt or 7 volt power supply to MAF TPS CTS IAT and many others so what ever hash may be present on the 12 volt positive supply simply gets chopped off
at 5 or 7 volts . no hash gets through , simple and effective .
some cars do the same on the ground side ,
early to mid 1990s 02 sensors ground on european cars comes to mind as an example ,
they have elevated ground to critical sensors , for the same reason .
so that gizmo
is as useless as mudflaps on a sledge hammer to you ,
but great for the seller , as it's sales can help to line his pockets with your money .
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