Fuel gauge problems. Cluster or sending unit ???

bmartinezx3

Original poster
Member
Apr 6, 2012
68
so last week i was moving and i noticed i was low on gas about 1/8 of a tank so i pumped $10 and when i got in it was at about 3/8 full. later that day i get in and it reads 3/4 (6/8) full. i didn't think of it too much till that night i got in again and it read completely full. before dropping the tank and changing the sending unit(fuel level sensor) i did the fuse 24 test and it fixed the problem. Then it happens again tonight, i pulled the fuse then put it back 20 min later and it appears to work fine again.

what could it be?

from what i hear a bad sending unit normally makes it show empty, and a bad cluster motor makes it stay in one place, so i have no idea what my problem would be. ANY help would be appreciated
 

Voymom

Member
Feb 3, 2012
2,523
I'm going to say its the fuel level sensor. I had the same problem in my Envoy. Its a pretty cheap part $30 IIRC. But the fuel tank has to be dropped.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
A bad sender doesn't have to always say empty. But one way to tell quickly if it's the stepper motor is if it returns to zero every time you turn the ignition off. A bad stepper just won't reliably go to zero. A scan tool that can look at the data stream is another way to see which unit is lying.

If it's your sender, call the dealer to see if your VIN is in the group that gets some help with the expense.
 

jrSS

Member
Dec 4, 2011
3,950
My sender is bad on my 07 SS......also had a bad one on my previous ride 06 envoy. Both vehicles would be innacurate and always go to E....then back up....and cycle continued. Also had the service engine soon light on both vehicles. Had my tranny fluid serviced and they scanned the ses light and told me the code # (don't remeber the #) and said it was a bad sender. I told them I knew it was a bad sender....blah blah blah. So hope this helps out. Dealer charge me $114 for 1st one and I called and now wanna charge me $150. They must grab prices outta their asses.
 

bmartinezx3

Original poster
Member
Apr 6, 2012
68
For some reason my OBD2 wont read, machine says its not connected. i called dealer and they said its a $500 job so i would pay atleast $250, another said $350 and another said $200. One dealer even said they wont touch the truck unless they run a $150 diagnostics test.

ill check to see if it goes back to zero
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
bmartinezx3 said:
For some reason my OBD2 wont read, machine says its not connected.
Your front fuse block fuse #13 is blown. Usually due to something plugged into your accessory/cigar lighter receptacle blowing the fuse. It's shared with the OBDII port, but the Owner's Manual never mentions it.
i called dealer and they said its a $500 job so i would pay atleast $250, another said $350 and another said $200.
It would be entertaining to ask them where the inconsistency comes from, since it should be a book rate job.
One dealer even said they wont touch the truck unless they run a $150 diagnostics test.
Another well-known dealer scam. Diagnosing it should be a 3 minute job inless they're staffed with incompetents (you don't want working on your truck anyway), and covered by the flat rate repair charge. If you call that dealer again, ask if the diagnostic charge will be rolled into the repair that GM picks up half of. What total BS they throw. :hissyfit:
 

jrSS

Member
Dec 4, 2011
3,950
They told me the same thing at another dealership. (The diagnostics bullshit) It is called BEN DAVIS chevrolet. We (everyone around here) calls it BENDOVER DAVIS. (Cuz ur def. gonna take it). Yup I just called u out BENDOVER.
 

bmartinezx3

Original poster
Member
Apr 6, 2012
68
the roadie said:
Your front fuse block fuse #13 is blown. Usually due to something plugged into your accessory/cigar lighter receptacle blowing the fuse. It's shared with the OBDII port, but the Owner's Manual never mentions it.

I had no idea, went to check it and sure enough it was blown. Thanks for the tip. i replaced it then got it scanned but it had no codes as of now. im thinking maybe the new fuse reset the codes so ill wait to see if they pop up soon.

might just pick up the sending unit at oreileys for $35 and drop the tank next weekend. hope that's the problem
 

bmartinezx3

Original poster
Member
Apr 6, 2012
68
now my oil pressure gauge is acting weird. so my voltmeter is completely dead, fuel gauge is off and oil pressure is reading incorrectly.
should i rebuild the cluster or look for an SS cluster? is it a straight swap?
 

Metalsmith

Member
Dec 23, 2012
13
My wife was hit in the rear bumber about a year ago and now the gauge will read empty right after refill ,but usually reads after a few start ups.... Does any one have a pic of where the ground wire is , as I know that redid all that in the repair.... don't want to lay under it, messing with a bunch of wires , there is a chance I could make it worse... ; )
 

Denali n DOO

Member
May 22, 2012
5,596
Metalsmith said:
My wife was hit in the rear bumber about a year ago and now the gauge will read empty right after refill ,but usually reads after a few start ups.... Does any one have a pic of where the ground wire is , as I know that redid all that in the repair.... don't want to lay under it, messing with a bunch of wires , there is a chance I could make it worse... ; )

Mine is a fuel sender unit issue that I have to change under GM extended warranty of 10 years 120,000miles, Mine goes to empty when it's full with light on and back to normal after about 50 miles, again mine goes to empty when below 1/4 tank. Mine sets the ses light with a code P0463. Probably your fuel sender unit.
 

woodja

Member
Dec 24, 2012
14
my fuel guage went haywire last week and plan to make the swap this new year weekend.
103,000 on the 06 and prefer to work on it myself as opposed to stealership even if GM would pay part of it. Something else always goes wrong when those guys touch it.

If its not too far off topic, advise on changing the fuel pump , level sending unit, pressure sensor as an assembly while i have the tank dropped?
Brand to avoid for the pump assy?
 

Metalsmith

Member
Dec 23, 2012
13
Denali....sounds like mine....2005 bought new in 2006, last one off the lot .....worked after all the repairs.... been doing this about a month ! After it starts reading right , it's good till refill..... where do I find about the extended waranty ..... Might even be able to claim unseen damage on the repairs !
 

Denali n DOO

Member
May 22, 2012
5,596
Metalsmith said:
Denali....sounds like mine....2005 bought new in 2006, last one off the lot .....worked after all the repairs.... been doing this about a month ! After it starts reading right , it's good till refill..... where do I find about the extended waranty ..... Might even be able to claim unseen damage on the repairs !

I can't find the thread to reference of hand. It's here somewhere. I don't remember what model year it started but it's 120,000 miles or 10 years starting from the build date on your door stickers. Most dealers will pay 50% of the repair cost, for me here in expensive Canada I gotta pay $250 or so. I also helped my friend change the fuel pump in an 03 TB, was a piece of cake to drop the tank and do the swap.
 

silverunicorn

Member
Dec 4, 2011
327
Reviving this thread, but what were your symptoms?

My fuel guage started doing wacky stuff after a starter replacement. Will fill up, and the guage will read E
Thanks,
Chris
 

BlazingTrails

Member
Apr 27, 2014
19,409
Is the orange indicator on as well? If it is it will be the sending unit. Very common on our trucks. This is the part that I purchased.


ttp://oooom.ebay.com/itm/360921256043?nav=SEARCH

It took about 2 hours to put it in and it has worked great for over a year now.
 

silverunicorn

Member
Dec 4, 2011
327
Yes. When I fill up, it reads "E" and the light comes on and the chimes ding. Will be like that but after a few starts it gets "normal" then can fluctuate from "F" to "E" in seconds.

What is strange is that all the ones at RockAuto are at least $177 (which includes the fuel pulmp). Is it better to replace that while you're at it?


It's super awesome!

Chris
 

JerryIrons

Member
Dec 20, 2011
434
Well, you have to take the tank off, and pull out the fuel pump in order to change the sender. Not a bad idea to replace the fuel pump as well, if you have a lot of miles on it.
 

silverunicorn

Member
Dec 4, 2011
327
That is what I was thinking as well. There is a huge discrepancy in pricing. Did they change somethign in 2006 that makes them more expensive?

I don't want to get from E-Bay. You never know where or what you're getting.

I was looking at ROckAuto and the cheapest is $170 and they go to $300. ANy difference in these really?

Chris
 

MAY03LT

Member
Nov 18, 2011
3,422
Delmarva
Chris, some 05+ guys are getting the sending the units replaced at no charge from an extended coverage policy. I don't have my notes in front of me but IIRC 10y/120k miles. It might be worth looking into.

If you do go the pump route, I'd go with bosch. They've proven themselves to me time and time again.
 

silverunicorn

Member
Dec 4, 2011
327
MAY03LT said:
Chris, some 05+ guys are getting the sending the units replaced at no charge from an extended coverage policy. I don't have my notes in front of me but IIRC 10y/120k miles. It might be worth looking into.

If you do go the pump route, I'd go with bosch. They've proven themselves to me time and time again.
Thanks. I guess I can try that, but I have 142K on the truck :sadcry:

Chris
 

silverunicorn

Member
Dec 4, 2011
327
Thanks Brandon -

How hard is it to et to this? I know you have to drop the tank, but how about de-presurizing the fuel lines? I an not a real wrench guy...would I be able to do this?

Chris
 

BlazingTrails

Member
Apr 27, 2014
19,409
It is easy start the truck and pull the fuel pump fuse, truck will stall out = no pressure. It is a little difficult to get some of the lines UN hooked, but once you get in there and get started it is easy to figure out. Just get the back of your truck up on jack stands, and use a floor jack and short 2x4 to put under the tank. Try to run all the gas out of it before you start.
 

JerryIrons

Member
Dec 20, 2011
434
I would have some of the connectors on hand for the fuel hose those plastic clips are easy to break. I have an ext and changed it myself with the tank half full of gas, it is easier if less gas in it. Also the fuel hose where it attaches to the tank, that might be tricky to get off, I think I ended up leaving the hose attached and seperating the other end. Either way you do not want to crack the plastic nipple that comes off of the tank and goes into the hose.
 
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BlazingTrails

Member
Apr 27, 2014
19,409
JerryIrons said:
I would have some of the connectors on hand for the fuel hose those plastic clips are easy to break. I have an ext and changed it myself with the tank half full of gas, it is easier if less gas in it. Also the fuel hose where it attaches to the tank, that might be tricky to get off, I think I ended up leaving the hose attached and seperating the other end. Either way you do not want to crack the plastic nipple that comes off of the tank and goes into the hose.
I agree, i actually detached the filler hose from the filler neck at the top. it was too difficult to get it off of the tank.
 

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