I want to reground my ECU at the harness of the ECU. The FSM for 1989 list pin 3A, 3B, 3C, 3D
as connected to "GROUND". In the Remark box to the outside, 3A & 3B states "POWER"; where as,
3C states "System" & 3D states "Analog.
Does it matter which one of these wires to the pins you use & what is the difference ? Just
guesing I'd most likley use 3A or 3B ?

Brad

 

When Mazda had a trouble shooting bulletin that added another gnd to the series four cars for a supposed AFM problem, they added it to the gnd wire for the boost/pressure sensor. That wire is common to most all the gnds for the sensors in the engine bay and atp on the series four.

I'd have thought the series five car would not have these problems. But if I were to add additional gnds to the ground wires of the ECU, I'd do 'em all. See the jpg. See pin 3C and 3D in the attached seires five schematic. They are connected to the same wires that the seires four TSB added a gnd to.