VTESPEED

Heres the problem:

2002 Z06 vette, car has something wrong in the engine wiring harness relating to the ground wire going to the back of the drivers side head.

The car keeps dying randomly and cutting out. It'll start and immediately die, sometimes itll run for a bit till it vibrates or you rev it up and the connection gets shaken.

I hooked up a fuel pressure gauge to the car, and everytime the car cuts out the fuel pressure drops and basically its like the fuel pump is shutting off due to the ground on back of head.

If I reach back and move the wiring I can make the fuel pressure cut on and off consistantly, Ive already taken the intake off and pulled apart the whole wiring harness and I cannot find a break or messed up wiring anywhere.

I would like to go to where ever the ground wire leads to and directly add a ground to it.


Where on the PCM or whereever does the ground wire on the back of the head go to?


The ground im talking about is G107 #11 on this picture

Cobra4B

I was about to tell you to check the ground and tighten the bolt, but it seems you've done that. Never heard of this problem and I'm sorry I can't help more.

Have you checked all the other grounds for corrosion etc?

VTESPEED

Its got to be directly caused by this ground im pretty sure.

If I push on the whole harness behind there while its running, it wont ever lose fuel pressure or die. If I pull on it and move it around I can make the fuel pressure gauge dance on and off basically so its something in there.

Ive checked every other ground on the car and made sure they are tight.


Basically If I can find where the ground wire going to back of the head goes I can tap into it somewhere near the pcm and add a ground to fix the problem I think.

Heres some pictures:

In the pictures, you will see that I have the ground on the back of the head going directly to a ground wire, going to the frame now as well trying to fix the problem.

vette.se

The ground connection on the back of the drivers side head got two wires, each one is black/white.These are not connected to the PCM, they go to the ignition coil package connectors - one to each side.

VTESPEED

Ive double checked all these grounds. Ive even regrounded the one to the back of the head to somewhere else...

The short is in the wiring harness group of wires behind the heads. If you look at the picture where you can see all the wires in the first picture, thats after I unloomed and opened it up looking for problems in it.

Drkjstr

I'm having the same symptoms, but haven't investigated as thoroughly, yet. Was this issue ever resolved?

Joseph Mazer

So the black wires (and there are two of them) that go to the back of the driver's side head are ground wires for your ignition coil. In order to get to where they go, you have got three move the intake entirely. The problem is, the EGR tube that goes from header on the driver side to the header on the passenger side has a mounting bracket that shares the bolt with these ground wires. It rattles loose, and now you're ground does not make a solid connection. You can do what I did which is remove the intake and put the EGR tube bracket back down and tighten it up or, you can simply cut those two wires and run a new ground at a different location. Doing it the right way was kind of a pain in the ***. And you are going to need, a pair of pliers, a pair of needle-nose pliers, an intake gasket set and patience.

Joseph Mazer

You can see the two black wires and the bracket for the EGR tube. The tube slips down beside the eye for the ground wires.
Due to limited space, this is where you were going to need some patients and a short 13 mm wrench

Cory51191

Where are those black wires coming from? Is there any way to access them to cut/solder another wire to relocate it? Or must the intake manifold come off to get to it?

C5 Diag

Each wire comes from C109/110 which then goes to G107 which are the coil grounds !!...pic enclosed !!

Cory51191

So in theory I could run the ground directly from that harness, to a good ground instead of the ground being located on the back of the head?

C5 Diag

In theory...yes !!

Joseph Mazer

I am not certain where it originates, I was just delighted to find the culprit and fix it! I ended up taking off my intake in order to get to it. I also had to bend a 13 mm in order to tighten the bolt effectively.

Cory51191

So if I check for continuity between the ground wire inside the coil pack harness & the cylinder head, and get a bad reading then I know those grounds are compromised correct?

C5 Diag

First thing is that checking grounds using "continuity" is NOT the proper way to check a ground...you must make sure that the wire can carry current back to the source...the battery !!...you must "load" the ground circuit as we say...let's say for instance ALL the wire strands are broken inside but one but when you do a continuity check it will be good...but can it carry current ??...NO !!...get yourself a headlight assembly with the power and ground wires attached at the parts store...I have a few different ones of varying wattages to check O2 heater circuits, fuel pumps, etc..you hook up the positive lead of the headlight to 12 volts and then connect the ground wire to whatever ground circuit you are testing...if the headlight is dim you have a high resistance in the ground circuit...if bright you're good to go !!!...I put an old pill bottle over the bulb because I was tired of dropping and breaking them...LOL !!!

Cory51191

Awesome! I’ll do this when I get a chance (probably next week) and I’ll report back. Thank you.

Joseph Mazer

What I did was locate The Wire, and while the car was running I wiggled the wire with a long screwdriver and when it shut off, I knew that was the problem. You should however be forewarned that they built the car around that damn ground wire

Cory51191

That ground appears to be good

but i did find a loose ground back there while i was fishing around.. mounted that to a good location and tested it.
and I found a 2-wire connector that I have no idea where it belongs.. wires are black and green