Fitness Stain

so i followed the write up that i got by searching "grounding how-to"

it tells me for an 88 TII to splice a ground into the blackwire on the plug of the pressure sensor ..

my black wire, was really two wires, ...
as there are 4 "slots" where wires go into on the plug for the pressure sensor ...

i assumed since both wires were black and went to the same slot, that they were both a ground ...

am i right?

RylAssassin

I have an FCD installed so i grounded mine to just the wire comming from the pressure sensor. Just follow the black wire from the pressure sensor and ground that not any other wire that flares out of it.

JamesWade2002

you retard that is not what he asked! If I were you fitness I would get a multi meter and check continuity on the wires in question. one of em has to have a beep. Then go for that one. I would not just ground any. Mazda does not really pay much attention to colors on their wire harness. some black with brown stripe is ground, some are O2 sensor stuff too. its wierd.

Fitness Stain

well , i didnt just ****** any wire ..

he said it was the black one, and there were only like 4 colors total includeing the black one ... it just kinda threw me off cause the only "slot" with black wires had two coming into it ... both black .. so i just soldered em both .. ill test em soon, and if ones not right ill just remove the solder, and retape

thanks for the reply james

NZConvertible

You need to undo what you've done ASAP. There is only one ground wire, and grounding one of the others will either blow a fuse (12v wire), fry the ECU (5V wire), or completely screw up the output (signal wire).

You need to clean the wires to confirm their correct colours. Looking at the back of the plug, they are:

12V: black/white (top left)
5V: brown/white (bottom right)
Signal: brown/red (bottom left)
Ground: black (top right)

If you have any doubt, you should be referring to a wiring diagram, not randomly soldering wires together.

WAYNE88N/A

Or randomly trusting any "grounding how-to" that instructs you to add a bunch of new wiring...

Fitness Stain

the only black wire was a split one

thats it ..
there were two wires going to one slot (both black)

i wasnt just randomly soldering things ...
it said solder the black wire ... so i did ... the only difference was that the slot with the black wire was really a slot with two black wires .. those were the only black wires

anyway ..

if i hook up a MM to those black wires ... for a ground i should i get 12V??

RylAssassin

I used this thread when i did my gorunding:
https://www.rx7club.com/showthread.p...ight=grounding
Its BlackRx7's thread and its in the ARCHIVE, im not just randomly grounding wires guys.
By the way after doing this my hesitation has almost completly gone away.

WAYNE88N/A

Dude, you're scaring me...turn the key off, put the multimeter on a resistance setting, clamp or place the black lead on a known ground (TB nuts work well), and put the red lead on that plug pin with the black wires (it doesn't matter if the plug is connected or not)...You should read ZERO or somwthing damn close, certainly less than 10 ohms or so...If you don't, it's not a ground, OR, the other original grounds on your car are ****...

Fitness Stain

thats the EXACT how to i used


he says .. on his 88 TII (which i have) its a black wire ..

well on mine there were 2 black wires .. both going to the same exact slot on the pressure sensor plug ...

i grounded both with one ground wire?

should i remove the solder and only do one?
if so what reading should i get from the ground wire with a MM?

Fitness Stain

by the way the engine has not been turned on since ive done this ...

so dont freak out people

WAYNE88N/A

If you sense any gains, imagined or not, after you add ANY ground wires, that is proof that the original grounds were in disrepair, and you would have accomplished the exact same results by cleaning them up...It's a part of preventative maintenance on our cars, right up there with repacking the wheel bearings, changing the PD, replacing the left heater hose, changing fluids, yada yada yada...

Fitness Stain

im completely aware of all this ... thats why im doing it in the first place

im simply asking what to expect when i put the MM to the wire that truely is the ground??

WAYNE88N/A

I told you- you should read ZERO ohms, or something damn close, if it's a good ground (I like using something on the engine itself for a ground (black lead) when reading from the chassis area- that way you're checking the engine bonding also)...BTW, be sure to have ALL power off the car every time you're reading resistances (ohms) with a meter...

RylAssassin

yeah you should get somthing less than 1 omhs. I got like .3 or somthing.

WAYNE88N/A

Here's a bit of useless trivia for you guys, maybe will help you understand things a little better...On an aircraft, the structure has to be grounded so well (called bonding), that a resistance reading from the radome (nose) static strips to the elevators (on the tail), a distance of over 100 feet, must be less than 100 MILLI-OHMS, or .1 ohm...If our cars are grounded that well, we'll never have any problems....

Fitness Stain

thanks guys

Fitness Stain

ok i just checked the resitance for the two black wires ..
i set my digi MM to 20K ohms (lowest i have) and both wires read the same 0.00

there is some flucuation at first ... but it settles at that point
i assume both are for the ground as they both connect to one of the four connections in the Pressure sensor plug

am i right to assume that?

Fitness Stain

and if both are indeed the ground, should i run seperate ground wires to both, or splice them together, and then run one ground or what?

WAYNE88N/A

Yeh, after all we've been through, I think for some reason you have a parallel ground circuit on the pin of that plug, but, for all practical purposes, you've found the ground (and a good one, at that)

Fitness Stain

so ground both wires, or just one?

if ground both wires, should i ground them individually, or just splice them together??

WAYNE88N/A

Doesn't matter- repeat after me: "A GROUND IS A GROUND IS A GROUND"...grounding both should be no better than grounding one- or better yet, clean up the existing ground that circuit goes to (not sure- could be the one below the air box there on the frame, or could be through the ECU)...

Fitness Stain

thanks mang!