Gas gauge not working properly why?

Tiny
ROSS SMITH
  • MEMBER
  • 2007 CHEVROLET SILVERADO
  • 200,600 MILES
I’m so happy to find this site. I have the truck listed above (classic). My check engine light came on recently. Then I noticed the gas gauge may register low. It may register accurate. It may be some where between. But I don’t think it ever registers more than what’s in the tank. I’m mechanically inclined but ignorant about this topic. I want to repair it myself. I put my programmer on it and got the code P0463. From my internet research, it could be a number of things from the cluster to a sensor on top the fuel tank. I’d like to narrow down my options to diagnosis it. Any suggestions? Thanks!
Wednesday, December 2nd, 2020 AT 2:50 PM

37 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Hi,

In the tank, there is a float that is attached to a rheostat. The rheostat sends a voltage signal to the PCM which goes to the BCM and then to the gauge. Ugh! A lot of things there.

I suspect the rheostat is bad or the float is going bad, However, If you look through the attached pics, they indicate the diagnostics for troubleshooting the issue.

Let me know if they help or if you have other questions.

Take care,
Joe
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Wednesday, December 2nd, 2020 AT 7:24 PM
Tiny
GREELEY SMITH
  • MEMBER
  • 2 POSTS
  • 2005 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 2WD
  • AUTOMATIC
  • 150 MILES
I have changed the instrument cluster and gas gauge will not give accurate reading
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Wednesday, June 2nd, 2021 AT 12:34 PM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
The info I looked at was for 5.3L vin B, single tank. The gage will default to empty if, the pcm detects a problem with sending unit circuit or if the ipc detects a problem with class 2 data from pcm.

You may be able to check gage reaction with resisters, get about three, 250 ohm--empty, 140 ohm--1/2 tank, 66 ohm--full tank. If the gage reacts correctly to each resister, I think the problem is the sending unit in the gas tank. If it doesn't react correctly could be a problem with pcm--ipc or wiring circuit.

The wire colors for the sending unit are black--ground, dark blue-- voltage. If you use a resistor between those two wire colors, key on, no need to start it, the gage should react. The voltage is a 5 volt ref circuit from the pcm.

You can get resisters from radio shack, don't cost much. You can also check for applicable trouble codes. Some of the national brand autostores will check codes for free. I just don't know if they will check manufacturer specific codes?
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Wednesday, June 2nd, 2021 AT 12:34 PM (Merged)
Tiny
GREELEY SMITH
  • MEMBER
  • 2 POSTS
Thank you. This was very helpful I will try this out.
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Wednesday, June 2nd, 2021 AT 12:34 PM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Hope you got it going your way.
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Wednesday, June 2nd, 2021 AT 12:34 PM (Merged)
Tiny
WKILMER
  • MEMBER
  • 2 POSTS
  • 2005 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 103,000 MILES
Fuel gauge dont work after changing pump?
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Wednesday, June 2nd, 2021 AT 12:34 PM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
In the info, notice the tank size in gallons, the specs may change depending on the size of the tank. That's where I would start.

It could be an issue with sending unit in tank? Don't know at the moment?
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Wednesday, June 2nd, 2021 AT 12:34 PM (Merged)
Tiny
WKILMER
  • MEMBER
  • 2 POSTS
Replaced the whole pump unit. Isnt the sending unit all part of that unit?
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Wednesday, June 2nd, 2021 AT 12:35 PM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
If the pump unit had the swing arm and float, then yes. You should be able to take the connector loose from pump assemble, use a resistor between proper two terminals, key on, see if gage reacts to resistor, try a couple resistors for full and low. The resistance spec is in the diagram. Radioshack sells resistors, don't cost much. If the gage reacts properly then the problem is either the sending unit or connector.
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Wednesday, June 2nd, 2021 AT 12:35 PM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Wanted to show sending unit circuit. Except hybrid.
Purple wire and black wire is for sending unit.
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Wednesday, June 2nd, 2021 AT 12:35 PM (Merged)
Tiny
JBETCHAN
  • MEMBER
  • 2 POSTS
  • 2001 CHEVROLET SILVERADO
  • 5.6L
  • V8
  • 4WD
  • AUTOMATIC
  • 220,000 MILES
Replaced the alternator. When I reconnected the battery cables the fuel gauge has pinged as far left as it could go and is now stuck (pointing at around 4 o'clock position). I've had no issues with the fuel gauge since I replaced the fuel pump six years ago.
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Wednesday, June 2nd, 2021 AT 12:35 PM (Merged)
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,492 POSTS
Hello,

The gas gauge does this when the circuit is open. Can you locate the fuel sender wire and ground it to see what happens? It is the purple wire going to the tank. With the key one please let me know.
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Wednesday, June 2nd, 2021 AT 12:35 PM (Merged)
Tiny
JBETCHAN
  • MEMBER
  • 2 POSTS
I was able to get the gauge working properly by disconnecting the battery for a few minutes. Thanks for the tip.
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Wednesday, June 2nd, 2021 AT 12:35 PM (Merged)
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,492 POSTS
Nice work, we are here to help, please use 2CarPros anytime.
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Wednesday, June 2nd, 2021 AT 12:35 PM (Merged)
Tiny
RON1700
  • MEMBER
  • 2 POSTS
  • 2001 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
I'm having trouble with the fuel guage on my truck, it will work fine sometimes, and sometimes when I start the truck it will be on empty, when I know that there is fuel in the tank. If I take it out of park and put it in neutral, and then back in park it will go back to normal. Have checked for loose wires and cleaned all the grounds I could find. Was hoping you could point me in the right direction!
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Wednesday, June 2nd, 2021 AT 12:35 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Hi:
Chances are the float level gauge is going bad. The only problem, it is part of the fuel pump in the tank.
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Wednesday, June 2nd, 2021 AT 12:35 PM (Merged)
Tiny
RON1700
  • MEMBER
  • 2 POSTS
Thanks for the reply! That's o.K. If it's part of the fuel pump.I just want it fixed! I kinda figured that was going to be the problem. Thank you for the help.
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Wednesday, June 2nd, 2021 AT 12:35 PM (Merged)
Tiny
DAUNNA
  • MEMBER
  • 3 POSTS
  • 2000 CHEVROLET SILVERADO
  • V8
  • 2WD
  • AUTOMATIC
The fuel gauge stopped working on my 2000 chevy silverado 1500
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Wednesday, June 2nd, 2021 AT 12:35 PM (Merged)
Tiny
FIXITMR
  • MECHANIC
  • 9,990 POSTS
Probably the fuel sending unit. Very common for this to fail on these trucks. It's in the tank.
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Wednesday, June 2nd, 2021 AT 12:35 PM (Merged)
Tiny
FIXITMR
  • MECHANIC
  • 9,990 POSTS
Pretty expensive dealer fix. Might also just be wiring problem. It's part of the fuel pump assembly which is why it's so expensive.
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Wednesday, June 2nd, 2021 AT 12:35 PM (Merged)

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