Where does Fuel Tank (Pump) Ground to Chasis

[John K86]

im trying to figure the location of where the ground wire that comes off the fuel pump grounds
To the chasis. It's a 2004 Yukon Denali.

...Or do I need the location of where the instrument cluster grounds?

I'm still working on a fuel guage that keeps getting stuck at Full. (And then eventually stuck at empty). It's not the cluster, pump or pump harness so I'm now searching for a loose or pulled ground wire. The latest time the guage got stuck at Full was when I had my car lifted to change my brake pads! Makes no sense- wondering if maybe the vibration loosens a wire.

 

[MrBalll]

It could be your sending unit or even the stepper motor.
How long has this been going on and when did it start? Like after a big bump or just randomly one day.

 

[John K86]

It could be your sending unit or even the stepper motor.
How long has this been going on and when did it start? Like after a big bump or just randomly one day.

You asked.....

Changed fuel pump few months ago when old one started leaking. Mechanic used AC delco. Worked when I left. Few weeks later got pegged on full (not past) after a complete fill up. I put in some Techron, went over a few bumps and banged the tank with a rubber mallet. Problem solved ..

2 months later stuck on full again after fill up. Mechanic dropped tank and tried another pump (outside of the tank). He moved float up and down by hand and it didn't change anything.

I changed the stepper motors myself (no change), tried another instrument cluster from a similar vehicle (same problem). About 2 weeks ago mechanic said you know what let me try a brand new AC delco pump and send the other back as defective. He dropped the tank and installed the new pump. I even provided them with a new wiring harness to attach the pump. Put backed together and worked for 3 gas cycles.

2 days ago I brought car in to change brake pads and rotors. When I got my car back- the gas tank was stuck on full again! I'm not saying it has anything to do with the pads but brainstorming if putting up on the lift and the vibration from taking off the rotors moved something that was loose!

I'm going crazy

 

[treehan77]

sub

 

[John K86]

sub

Sub?
As in the subwoofer?

Please elaborate!

 

[treehan77]

Subscribe - just following the thread waiting for an answer

 

[retiredsparky]

There is no external ground. The fuel gauge is wired directly to the PCM. The PCM provides what is called a low reference, probably a ground, which is a black wire(PCM terminal C-1 #23). The signal wire that controls the fuel gauge is purple (PCM terminal C-2 #54).

According to the wiring diagram gods, that cable runs from tank to PCM with no change in the color of those wires.

A multimeter should read 40 ohms between the wires at the tank when full, 250 ohms when empty. (Disconnect the harness before checking).

If you can figure out where the fuel pump/gauge is located under the floor board, you could consider cutting a hole for access. I have done this on multiple vehicles instead of lowering the tank. It does require some care to avoid cutting wiring.