tomw wrote:WPTSKI said:
If it's a signal ground or a return path, it's a floating ground and should originate at/from the PCM.
Okeydoke. What does "floating ground" mean?
My impression is that a signal ground is a more direct way to have a 'common' ground point, with similar resistance, save wire resistance, to a ground plane as the CPU sees. If you were to ground computer parts to individual grounds on a ship, as I had experience with, you ran the risk of having a 'ground loop' whereby the 'ground' at the cpu was different from the 'ground' at the tape units or printer. Just the difference in resistance caused by the path length and other variables could induce currents that were not desired.
Do you mean that the floating ground is not connected anywhere to the chassis ground? That would leave it 'floating' with respect to chassis ground, but leave it susceptible to bad stuff happening if it WERE to become 'ground' for something undesired. If you lost headlight ground, and there was a signal ground handy, the current through that signal ground could fiddle with 'stuff', no?
Floating ground is using a seperate wire for signal return path. Instead of one hot wire and using chassis ground to complete the circuit, a seperate wire is used. For instance that's the way the electric clutch in the rearend on the 4WD is powered. Probably because it a pulse width modulated(PWM) signal. Early O2 sensors were only one wire and used chassis ground but I guess that didn't work too good.
The DRL is PWM as well because it's a reduced output, soooo the whole system could be PWM. Nothing is simple anymore!
BTW: I was a ETN lllloooonnngggg time ago!