Fuel Guage - Got my Escalade Cluster

[GMCYukalade]

its inside the cluster - all it is is a shell, w/ something inside of it, wrapped in copper wire... so i'm guessing its an elctro-magnet... - and the purple wire is susposed to send it one voltage constant.. w/ a higher or lower OHMs.. but, its sending like different ohms constantly causing it to vibrate

 

[treepete]

can the DC pulsing cause the field of that inductor to collapse, and cause the jitter?

 

[95TwinTT]

If we make the assumption that the ECM is not damaged, then the pulsing is normal and the gauge must operate similar to a audio VU LED meter, where pulses hold the reading in the appropriate position and removing the pulses causes the guage to return to the bottom with a damper slowing the action.

If the guage worked like the old fashion gas guages, there would only be one wire from the tank sending unit, going directly to the gauge.

This fuel guage has a + 12volt connection, a ground and a signal wire that provides the pulses from the ECM.

The fuel sending unit wires go to the ECM, so it has to be digested by that computer and the signal that sets the gauge level, comes out over that purple wire.

Why it is not working all of a sudden, must be because the gauge itself is damaged or the ECM is damaged.

Is there a chance that + 12 volts got sent down that purple wire to the ECM?

I'm running out of ideas here.

 

[GMCYukalade]

no, ive never sent anything down the purple wire - alot of people seem to have the same problem as i.. so i was hoping it isn't the ecm... the Fuel guage just vibrates.. - now on my old cluster the fuel hand vibrated it's self to an early grave.. thats why i replaced clusters - but, its just going to do it again.. so.. i guess it is the ecm? that or something is taping into that wire - but if that happened it would also send feed to the ecm.. causing a problem in both places

 

[95TwinTT]

How about unhooking the fuel sender line to the ECM. Just to make sure it is not doing something wierd. If you can't find a connection that is easy to get at near the tank, you could pull C-3 from the computer.

The purple wire comes out of C-1, check and see if that same pulse is happening after the sender is unhooked.

 

[GMCYukalade]

you know, i unhooked the black wire from the fuel tank before i had to put in the 3rd new sender unit (i put one in two weeks before i had to put the 2nd one in it) and upon un-hooking that wire - the fuel hand still shook pretty bad, and then after about 3 miles.. it just stopped - i know this isn't the purple but it is the black, and both wires go to the float in the tank.. so i'm going to assume that both run to the ecm - because the Small black w/ white stripe doesn't run to the frame ground, like the big thick black wire does for the fuel sender.. its, big black, big grey, small black w/ white lead, and purple.. if i do remember correctly (i have another one of these wiring harnesses in the garage.. i can get it if you need to know the specific colors - they gave me another one w/ the 2nd new pump) - but, yeah, i'll un-hook the purple one asap - right now it is 9:42pm here - just got home from Church.. so it may be tomm. evening before i get to it, right after work..

 

[95TwinTT]

The wires from the sending unit should be purple with white stripe and black with white stripe. The black with white stripe is signal ground. Not the same as 12 volt ground for the rest of the car.

There can be another wire involved if you have two tanks. That would be a gray wire which is 5 volt reference. All three of them are inputs to the ECM.

Both the purple with white stripe and the black with white stripe are needed to complete the signal to the ECM.

 

[GMCYukalade]

Ok. ya.. i unhooked the black just for a little while.. well untill i put a new sender in it.. because the fuel hand had already went crazy, and was over on my oil guage... so i wanted to see if that would make it stop spinning.. - Let me tell you everything that happened from the beginning

Well, i have had 4 rear-ends come out of this thing.. and i was running lean on money so i left it set for awhile - i finally put a rear-end in it that i found in a junk yard setting in a 96 tahoe.. and i put two new batts in it because after setting for two years the old interstates kicked the bucket.. so i had it back up and running good, changed the oil etc.. and then i noticed my fuel hand issue.. i thought after letting it set that long the float probably had dead spots on it... so i didn't pay it any attention.. - well dad and i had planned on going to the AutoFair in Charlotte so, i filled the tank up in the kon and thought that would be a good time to test the new rear-end out - drove about 40 miles.. and all of a sudden my fuel hand starts doing circles clockwise extremly fast, hitting the oil guage.. i could turn the key off, and then turn it to on so the oil guage wasn't registering and the fuel hand looked like a extremly fast clock... well.. that kinda got old - while i was at the parts meet i picked up a fuel guage for GM.. - well i was told by my dealer that it was the fuel sender unit.. so i replaced it, its under warranty anyways.. put the new one in.. and no change.. except for the fuel hand just stuck in one spot, and from time to time, it would go counter-clockwise really slow.. so checked back with the dealer, they told me its the gauge cluster itself.. so.. i bought one of those.. and it went back to being its old self.. w/ the vibrating issue like it was before it started spinning.. so - and then my new fuel pump went out.. so i had to replace it again.. still no changes in fuel hand - new wiring on pump - however - there was one pic that you will see the new clusters fuel hand got stuck WAY over, and so did the oil gauge.. no clue what that was about, both of them are working now, except fuel hand is vibrating.. and i just don't want it to start spinning again.. - When-ever i turn the key to the on position before cranking the kon, the fuel hand JUMPS all the way past full, and then back to e and then it starts to register fuel.. and i figure this is probably what made the old one go out.. the jumping its like it sends to many ohms to it when you first turn it on i still haven't had a chance to throw the ohm meter on it.. but i will tomm. right after i get off of work

 

[95TwinTT]

Am I on candid camera?

If not, I can tell this is going to be a challange.

We need to get back to basics here. There is a very good chance that the entire fuel sending unit and gauge are 5 volts. I can't tell for sure with my borrowed schematic.

Was the wiring disturbed with the rear end change out's? As far as you know was there ever a 12 volt line that could have either touched or crossed either of the sender wires?

The fuel tank sensor shows that it is just a variable resistor, but not to ground. It varies the resistance "in line" with the black, or black with white stripe and the purple with white stripe. If that is the case, the black wire should have voltage on it and the purple should be the signal in to the ECM.

You could prove that quickly by checking for voltage on pin 19 of C-3. If that shows +5 volts, if you jumped that to pin 13 of C-3, the guage should read either full or empty.

You have enough variables that several things could have gotten whacked at one time or another.

It is kind of pointing towards the ECM being the culprit here.

 

[GMCYukalade]

nah, the only things that i found w/ rear-end swaps are the e-brakes are a PAIN! i'll find out everything tomm. about voltage, and what happens when i un-plug the purple wire from the fuel sender... and i'll go from there

 

[95TwinTT]

It might be easier to do the voltage readings at the ECM. The schematic say's it is on the left side of the engine compartment. The pin numbers will probably be hard to read, but these wire colors should make it easier.

There should be four plugs on the ECM.

Here are some "pin out's" with wire color's

Out to fuel guage. plug C-1 Pin 9 Purple

Vehicle speed sensor Plug C-1 Pin 29 Light green / with black stripe

Vehicle speed sensor Plug C-1 Pin 30 Purple / with white stripe

5 volt reference Plug C-3 Pin 27 Gray

Fuel Senor R TRN Plug C-3 Pin 19 Black

Fuel Sensor "fuel in" Plug C-3 Pin 13 Purple / with white stripe

So the things to check would be first is there voltage on C-3 19, if so, with C-3 unhooked from the ECM, is there a signal on C-1 9? If not, does that signal change on C-1 pin 9 if if C-3 13 and 19 are jumped?

This could quickly give an indication if the ECM is OK. Just be very careful of the pin out identification. It is better to go very slowly in these areas.

 

[GMCYukalade]

Well, everything seems to be fine from gas tank in.. its coming back out of the ECM where things are getting messed up.. - Fuel hand purple wire.. jumps from 0 - 8volts when key on... than settles on 3.63 (guessing this is how much fuel is in tank) and sets and goes 3.63 - 3.64 - 3.65 - 3.63.. causing the vibrating gas needle..

Which leads me to a new question has anyone on the 96-99 platform tried the new ECM swap.. the one out of an 2000, 2001 Express van? the 0411

 

[chevylee]

Hey I have been looking for that type of cluster for my 98 chevy truck. The 100 mph just isn't enough haha. Were did you pick yours up at??

 

[GMCYukalade]

www.car-part.com - when you ge there and perform a search, use 1999 chevy escalade - and use part type set it as Speedometer - now, go to like the 9th page and you can find em pretty cheap mine was like $50 bux after shipping

 

[chevylee]

Wow, thanks a bunch. Though I would have to spend 200 or so on one.. do you know if there is anyway to have the mileage fixed on it?

 

[GMCYukalade]

um ... please PM me

 

[chevylee]

Found a nice one, thanks PM sent.

 

[chevylee]

Oh btw did you get your fuel gauge working? It probably is the fuel sending unit.

 

[GMCYukalade]

no its not the sending unit at all... - its the PCM..

 

[chevylee]

no its not the sending unit at all... - its the PCM..

How weird is that.. Did you have to use a credit card when buying yours? I hate using mine, i rather use pay pal but they don't accept it.