Fuel gauge sending wire disconnected= normal engine performance?

[1998_K1500_Sub]

I noticed in one of the drawings that G103 shares a common connection with G150 to a single stud on the engine.

@2jduenas, is that actually the case on your engine?

Does anybody know where G150 goes?

For some reason, it may be important that G150 is grounded to the same stud as G103.

 

[2jduenas]

Remove the ”C” connector from the ECU and probe the ECU pins directly with a DVM.

By the way, if you have not removed that ground connection to the chassis at the fuel sender using the small black wire, you should do so now or very soon. That connection should be eliminated.

It sounds to me like that connection, the small black wire at the fuel sender which is a sensor ground connection to ECU pin C19, was actually functioning as a system ground in lieu of G103 and G104. How exactly that was happening isn’t yet clear to me. I know you have found at least one ground connection (G103 or G194, yes?) that was not in place.

Ok will do and as for the small black wire, I only jumped the to the frame to see what reaction I’d get but has been removed since, the only ground still connected at the fuel tank area is the factory ground for the fuel pump.

 

[2jduenas]

I noticed in one of the drawings that G103 shares is a common connection with G150 to a common stud on the engine.

@2jduenas, is that actually the case on your engine?

Does anybody know where G150 goes?

For some reason, it may be important that G150 is grounded to the same stud as G103.

I found this see image, looks like it’s on the same stud as G103

I noticed in one of the drawings that G103 shares is a common connection with G150 to a common stud on the engine.

@2jduenas, is that actually the case on your engine?

Does anybody know where G150 goes?

For some reason, it may be important that G150 is grounded to the same stud as G103.

 

[2jduenas]

I found this see image, looks like it’s on the same stud as G103 and the answer is no it does not appear there’s a G150 on my truck however I just found this by looking up my exact year and model…. Could this mean I may have another missing ground? I’ll look at the back of the alternator in the morning.

 

[1998_K1500_Sub]

You might want to verify that there IS a G105 wire on your truck, and then give consideration to where it is connected.

You may wish to go to the service manual to identify / locate all ground connections in the engine bay, and then confirm that they are in place on your truck.

 

[Road Trip]

Does anybody know where G150 goes?

For some reason, it may be important that G150 is grounded to the same stud as G103.

Good question. I went through all 4 volumes of the '98 FSM, and also checked the '99 FSM too.
To be honest, it looks like the "G150" ground is part of the noise floor of the service manuals?
That is, it is an error in that illustration that wasn't caught during final proofreading?

To convince myself that the G150 reference was a mistake, I scanned Vol. 1 of the '98 FSM
for how many times that each of the following grounds are referenced, whether in the DTC
troubleshooting flows and/or in the wiring diagrams.

Ground - total number of references:
G103 --- (30)
G104 --- (35)
G105 --- (25)
G150 --- ( 2)

In essence, the G150 we saw in the illustration was not seen elsewhere in the troubleshooting flows.

To build confidence in the above, I decided to Search the entire GMT400 forum for these same
grounds and count how many replies contain them:

Ground - total number of replies
G103 --- ( 28)
G104 --- ( 29)
G105 --- ( 31)
G150 --- (6 3) Note: 3 are from this thread. The other 3 are from another thread that dead-ended prior to a successful resolution.

Given the above, I suggest that for now we should sideline any references to 'G150'.
NOTE: Circuit #150 is used to document the wiring of several ground circuits in the FSM, so it's possible that G150 was
a naming error taken from a ground circuit #? (See 1st attachment) Which in turn begs the question - if there's actually
a 3rd ground wire in the vicinity, what would it's proper name be?

To summarize, G103/104/105 are legitimate grounds, regularly referenced in DTC descriptions and troubleshooting flows.

G150 looks to be an orphan entry in an illustration in the '98 FSM. (See 2nd & 3rd attached for differences between '98 & '99
454 ground illustrations.)

That's all I've got. If anyone can find a legitimate reference to G150 in the FSMs then
please don't hesitate to add it here. (I consider myself a student of the FSMs and I'm
still learning them myself.)

FWIW --

 

[Road Trip]

Adding a real world 'known good' perspective to reply #46 above.
Disclaimer: These photos are taken from my '99 454 C2500:

You must be registered for see images attach

Note: Black w/white stripe visible on G104, and is also referenced on previous wiring diagrams. Not currently in concours condition, these
grounds are as found, ~222K miles, and operating with excellent starting, good driveability, no SES light or DTCs. (A 'known-good' example. See
attached for individual detail photos of G103 & G104.) This upcoming weekend I hope to pull the C3 connector off of my VCM and get a couple
of 'known good' ohm readings of these grounds for future reference. I'll be sure to post them to this thread.

NOTE: If anyone reading this has photos of the grounds on their '98 454 (especially if you have 3 ground wires) then please add them to this
thread. I'd really like to get the big block <> VCM grounding physical implementation fully documented for reference purposes.

****

PS - Later this evening I'll write up some possible ways to go from the 'ground verification' step to the next step in troubleshooting this problem.

Cheers --

 

[phantom 309]

I have no dog in this race,. my comment is kudo's to all the intense research by members to help unselfishly.
Second comment,. ground is ground,. i have use a set of booster cables on numerous occasions with both cables connected to ground right at battery and 1 clamp to engine,. and another to frame rail.
I noticed the C3 connector actually has 4 grounds? ,.#4 pin

 

[1998_K1500_Sub]

Second comment,. ground is ground,.

Yeah… not really.

What most people call “ground” is actually a multitude of parallel, relatively low impedance paths.

The only mistake in your statement is that some of these “low impedance” paths have relatively higher impedance than others, and that’s where unexpected problems can arise if one assumes “ground is ground”.

This may go against intuition, but it’s the truth

 

[Road Trip]

I noticed the C3 connector actually has 4 grounds? ,.#4 pin

Eagle eye, @phantom 309! Multiple sets of eyes reading for comprehension is what makes this
forum the strength that it is. I appreciate you studying the contents of this thread so carefully.

I'm going to edit/correct reply #35 now so that it's a better resource for future reference.
(EDIT: Fixed.)

Well done, sir.