Please Help Me Identify ECU Ground(s)

[Captain Obvious]

I have some questions regarding ECU ground that I could really use some help with:

1. Where does the power supplied to the coil packs ground at? I'm assuming since the coil packs are powered by the coil drivers inside the ECU, the answer is ECU ground.

2. There is a small, short chassis ground wire right next to the ECU box itself. Does this solely constitute ECU ground, if at all?

3. There are two small black ground wires coming out of a pigtail under/near the fuse box, both of which follow along the battery ground cable and ground at the battery. One of these black ground wires also grounds to the chassis along the way. Is this the ECU ground wire? Or the other? Or both?

Any information provided here will be greatly appreciated.

[311-420]

You might find one of these helpful.

http://m.ebay.com/itm/2004-Ford-Must...257Ciid%253A14

[Captain Obvious]

Wow! I might have to pull a Chris Rock I'm Gonna Git You Sucka-maneuver and see if that dude will sell me just the pages I'm interested in.

On a serious note, I hope this doesn't come down to pulling that trigger.

Thanks, 311-420, for making me aware such a purchase is even available.

[311-420]

Originally Posted by Captain Obvious

Wow! I might have to pull a Chris Rock I'm Gonna Git You Sucka-maneuver and see if that dude will sell me just the pages I'm interested in.

On a serious note, I hope this doesn't come down to pulling that trigger.

Thanks, 311-420, for making me aware such a purchase is even available.

He may sell you the small book with the wiring diagrams. Id be surprised if he took pages out and sold them separate. But who knows.

Nice build you've got going! Don't be such a stranger.

[DSG2003Mach1]

i dont know what grounds control what but yes theres that factory ground @ the PCM.
there are 2 at the radiator support by the battery. There is one at the radiator support on the pass side. There is a ground strap from the motor mount to the frame rail.

edit: someone is supposedly uploading a manual to me with wiring schematics. If its correct Ill pm you and add you on dropbox (60something mb file)

[Captain Obvious]

Originally Posted by 311-420

He may sell you the small book with the wiring diagrams. Id be surprised if he took pages out and sold them separate. But who knows.

I was only kidding...couldn't help but think of the Chris Rock skit where he tries to buy just one rib and a handful of soda, then whips out $100 bills to pay.

Originally Posted by 311-420

Nice build you've got going! Don't be such a stranger.

Thank you! I plan on sharing the build once I resolve all of my gremlins and actually get somewhere. This ground issue I've been contending with should be the last of them.

[Captain Obvious]

DSG2003Mach1, thank you in advance!

I'm going to look all the chassis grounds over, follow the wires, and check pigtail connections.

[Captain Obvious]

DSG2003Mach1 delivered.

On page 4180 of 4378 in the official 2003 Ford Mustang shop manual, I found the PCM ground information I was after:



I went ahead and annotated this diagram, in lieu of all my observed issues and the probable culprit:



I'm hoping to work on the car this weekend and go for another test drive. I'm currently 0 and 4 with this issue. I don't expect I'll be going 0 and 5. And I think I'll stick with my original PCM, which probably isn't damaged after all.

If anyone else would like a copy of the referenced shop manual, you can download it here.

[DSG2003Mach1]

Glad I could help, it's a 60+mb file as a warning