Ground
- Thread starter Mafia Mustang
- Start date
Ok dumb question guys. There is a ground coming off of my harness. What could be the effects if I didnt hook this ground up?
If it attaches to the back of the intake manifold and it's made of some kinda stainless braided wire material, that's one of your primary engine grounds. Yes, you should ground it. Will your car run without it? Probably ... but probably not as well as it should. I found one little seemingly innocent ground wire hanging around limply behind the rear of my motor while doing my clutch swap a long time back, and lo and behold, hooking it up got rid of my annoying intermittent power-loss/backfiring issue - turns out it was the ground wire that went into the bundle of wires for my fuel injection harness. (Umm ... oops. 
)
You could hook it back up to the firewall/intake and call it done ... OR you could do one better and ditch that stupid braided wire crap in favor of a beefy 4-gauge battery cable with soldered-on/sealed lugs on the ends.
)You could hook it back up to the firewall/intake and call it done ... OR you could do one better and ditch that stupid braided wire crap in favor of a beefy 4-gauge battery cable with soldered-on/sealed lugs on the ends.
OK, well I grounded the wire to the back of the lower intake. Yes hissin it was a tan or orange. Still not getting any respone from my code reader though. My rpms only go to 3500 before the engine light comes on and kicks the rpms back downim gonna try an post a video to show yall what im talking about. Could this problem be vacuum routed wrong or overtighten rocker arms?
Computer will not go into diagnostic mode
How it is supposed to work:
The black/white wire (pin 46) is signal ground for the computer. It provides a dedicated
ground for the EGR, Baro, ACT, ECT, & TPS sensors as well as the ground to put the
computer into self test mode. If this ground is bad, none of the sensors mentioned will work
properly. That will severely affect the car's performance. Since it is a dedicated ground,
it passes through the computer on its way to the computer main power ground that terminates at the
battery pigtail ground. It should read less than 1.5 ohms when measured from anyplace on the
engine harness with the battery pigtail ground as the other reference point for the ohmmeter probe.
What sometimes happens is that it gets jumpered to power which either burns up the wiring or
burns the trace off the pc board inside the computer. That trace connects pins 46 to pins 40 & 60.
Only an experienced electronics technician can open the computer up & repair the trace if it burns
up and creates an open circuit.
The STI (Self Test Input ) is jumpered to ground to put the computer into test mode. Jumpering
it to power can produce unknown results, including damage to the computer. The ohm test
simply verifies that there are no breaks in the wiring between the test connector and the computer input.
How to test the wiring :
With the power off, measure the resistance between the computer test ground
(black/white wire) on the self test connector and battery ground. You should see less than
1.5 ohms.
If that check fails, remove the passenger side kick panel and disconnect the computer
connector. There is a 10 MM bolt that holds it in place. Measure the resistance between
the black/white wire and pin 46: it should be less than 1.5 ohms. More that 1.5 ohms is a
wiring problem. If it reads 1.5 ohms or less, then the computer is suspect. On the
computer, measure the resistance between pin 46 and pins 40 & 60: it should be less than
1.5 ohms. More that that and the computer’s internal ground has failed, and the computer
needs to be replaced.
If the first ground check was good, there are other wires to check. Measure the
resistance between the STI computer self test connector (red/white wire) and pin 48 on
the computer main connector: it should be less than 1.5 ohms. More that 1.5 ohms is a
wiring problem
The following is a view from the computer side of the computer connector.
Diagram courtesy of Tmoss & Stang&2birds
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine
How it is supposed to work:
The black/white wire (pin 46) is signal ground for the computer. It provides a dedicated
ground for the EGR, Baro, ACT, ECT, & TPS sensors as well as the ground to put the
computer into self test mode. If this ground is bad, none of the sensors mentioned will work
properly. That will severely affect the car's performance. Since it is a dedicated ground,
it passes through the computer on its way to the computer main power ground that terminates at the
battery pigtail ground. It should read less than 1.5 ohms when measured from anyplace on the
engine harness with the battery pigtail ground as the other reference point for the ohmmeter probe.
What sometimes happens is that it gets jumpered to power which either burns up the wiring or
burns the trace off the pc board inside the computer. That trace connects pins 46 to pins 40 & 60.
Only an experienced electronics technician can open the computer up & repair the trace if it burns
up and creates an open circuit.
The STI (Self Test Input ) is jumpered to ground to put the computer into test mode. Jumpering
it to power can produce unknown results, including damage to the computer. The ohm test
simply verifies that there are no breaks in the wiring between the test connector and the computer input.
How to test the wiring :
With the power off, measure the resistance between the computer test ground
(black/white wire) on the self test connector and battery ground. You should see less than
1.5 ohms.
If that check fails, remove the passenger side kick panel and disconnect the computer
connector. There is a 10 MM bolt that holds it in place. Measure the resistance between
the black/white wire and pin 46: it should be less than 1.5 ohms. More that 1.5 ohms is a
wiring problem. If it reads 1.5 ohms or less, then the computer is suspect. On the
computer, measure the resistance between pin 46 and pins 40 & 60: it should be less than
1.5 ohms. More that that and the computer’s internal ground has failed, and the computer
needs to be replaced.
If the first ground check was good, there are other wires to check. Measure the
resistance between the STI computer self test connector (red/white wire) and pin 48 on
the computer main connector: it should be less than 1.5 ohms. More that 1.5 ohms is a
wiring problem
The following is a view from the computer side of the computer connector.
Diagram courtesy of Tmoss & Stang&2birds
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine
