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Anonymous Posted on Jan 08, 2018

My gas gauge is stuck on full. I've replaced the sending unit and have check all the wireing and nothing works what can it be?

I swapped the dash cluster from my Yukon over to the truck and the one from my Yukon jumps right on full but the cluster from my truck into my Yukon works fine. Also when you shut off the ignition switch it still stays on full. I've tried everything and I'm stuck. Any help would be great.

1 Answer

Jeff Armer

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  • GMC Master 15,575 Answers
  • Posted on Jan 08, 2018
Jeff Armer
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It helps to know how it works ! The fuel level sending unit is a input to the VCM - engine computer . The VCM needs this info so it can do evap. emission leak detection testing ! The VCM sends this info. to the instrument cluster via the class 2 serial data network .
U.S. Federal regulations require that all automobile manufacturers establish a common communications system. This vehicle utilizes the Class 2 communications system. Each bit of information can have one of two lengths, long or short. This allows the vehicle wiring to be reduced by the transmission and reception of the multiple signals over a single wire. The messages which are carried on Class 2 data streams are also prioritized. In other words, if two messages attempt to establish communications on the data line at the same time, only the message with the higher priority will continue. The device with the lower priority message must wait. The most significant result of this regulation is that the regulation provides the scan tool manufacturers with the capability of accessing the data from any make or model vehicle sold in the United States.
Hooking up a factory tech 2 scan tool to view sensor data inputs to an from the VCM an checking for DTC'S - diagnostic trouble code's is the proper way to diagnose .
DTC P0462 Fuel Level Sensor Circuit Low Voltage
DTC P0463 Fuel Level Sensor Circuit High Voltage


The Fuel Level sensor is an important input to the VCM for the Enhanced Evaporative System Diagnostic. The VCM needs the fuel level information in order to know the volume of fuel in the tank. The fuel level affects the rate of change in the air pressure in the EVAP system. Several of the Enhanced Evaporative System Diagnostic sub-test are dependent upon the correct fuel level information. The diagnostic will not run when the tank is greater than 85% or less than 15% full. (This sensor signal disables the misfire when the fuel levels are less than 15%). This DTC is a type D DTC.

Action Taken When the DTC Sets
• The control module stores the DTC in history after the first failure but will not illuminate the malfunction indicator lamp (MIL).

Your best bet , take it to a qualified repair shop.

5 Related Answers

Molson02536

Harvey N Tawatao

  • 3854 Answers
  • Posted on Sep 04, 2009

SOURCE: 2003 GMC Yukon - fuel pump

Check your ECM fuse. There should be 2 fuses for your ECM. It's the ECM that controls the function of the fuel pump. Good luck friend and it's also common for the wire harness from the frame to the fuel pump to go bad due to corrosion from the bad weather we get in the winter and rainy spring and fall. 

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Anonymous

  • 5158 Answers
  • Posted on Mar 18, 2009

SOURCE: 2002 GMX Yukon Denali XL will not start and battery has a charge.

get a boost to start it. after you start it let it charge up the battery on it's on. if it does not charge the alternator might be defective.

Anonymous

  • 6784 Answers
  • Posted on Jun 22, 2009

SOURCE: fuel gauge inop on 2005 envoy

Hi, this is a sending unit issue. you can try adding some Sea Foam additive to the tank. this may release the sender. if the additive doesn't work, replace the fuel level sending unit.

Anonymous

  • 1608 Answers
  • Posted on Dec 18, 2009

SOURCE: 2004 Yukon XL Denali fuel gauge fluctuations

You can get the codes checked and see if you have a level sensor code.The level sensors are known to go bad on these vehicles.Sometimes when you rock the vehicle it will start to work properly.What happens is the fingers on the level sensor wear out and it works erratically.You can get the level sensor separately from the fuel sending unit.Hope this helps.Good luck.

Anonymous

  • 90 Answers
  • Posted on Dec 31, 2009

SOURCE: I have an '02 gmc yukon, stuck in 4 low.

Check for a blown fuse. use your manual to find fuse location. you can remove the shift motor and engage it manually, you need to remove front driveshaft.

Testimonial: "thanks for the help, wasn't what i wanted to hear, but oh well. At least we have a good GM dealer here. Happy New Year!"

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I have a 03 Camry the gauges are all working but the gas gauge reads full all the time is there a separate fuse for the gas gauge ? How can I fix this problem?

The sending unit is on the fuel pump and could be stuck in the full position. There is no separate fuse for the gas gauge. I think you will need to check the wiring from the fuel pump where you can for breaks, cracks in the insulation and also, check the ground. If that looks ok, pull the fuel pump.
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The temp gauge and battery light issues may not have been related.
The gauge reads high when the circuit to the temp sending unit is grounded. It could be the gauge on the dash, or a wiring problem, or the temp sending unit on the engine.
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Usually the sending unit is not connected, the sending unit is stuck on full, or the gauge on the dash is faulty. You would unplug the harness at the tank and check the circuit for power from the gauge.
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The most common way to find out is to test both components.
The sending unit in most vehicles grounds the gauge on the dash.
You would unplug the sending unit - pump harness at the tank and ground the sending unit wire. If the gauge climbs up to full the sending unit is at fault.
You could also measure resistance in the circuit in the tank when the tank is close to empty and after filling it up. The resistance should be different each time.
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It may be the sending unit in the tank that needs replacing. Here's how you can check: Turn the key on and disconnect the sender unit at the gas tank. Ground the sender unit's wire with a jumper wire from the truck's harness to ground. Watch the gauge. If the gauge on the dash is good, grounding the sender wire will cause the gauge needle to react and should move to full. This would indicate a new sending unit is required. If the gauge doesn't move when the sender unit is grounded, the gauge is bad and needs replacing. Pull the instrument cluster out to replace the gas gauge. Likely any old ford gas gauge might work-back then, there were not so many production changes.
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If the sending unit was connected and grounded, I would guess the gauge in the cluster is faulty.
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Gas gauge don't work. says it's full all the time. new sending unit,gastank,fuelpump, and fuel fiter.

I don't have the specs on your dash gauge. You would want to run an OHMmeter to test resistence at the dash gauge, then check the Ohms at the wiring from the fuel sending unit. The change in the Ohms from the fuel tank is what moves the dash gauge.

Best I can help with is a chassis diagram at Autozone.com, FREE, when you register your car.

You can go to a Salvage yard with an Ohmmeter and test a fuel gauge on-the-car to see if it has different resistance. This would indicate whether your gauge is good or not.
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I have a 2003 GMC Envoy and my gas gauge has been flowing up and down to empty and full recently it has stayed on empty. How do I fix it?

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  • 2 Check your fuel gauge fuse if the gauge's indicator stays on empty when your turn on the ignition. If the fuse is good, join the sending unit connector to ground. Replace the sending unit if the gauge indictor moves to the full line.
  • 3 Ground the terminal located on the back of the fuel gauge with a jumper wire if the indicator doesn't move. If it does move, consider replacing the wire between the fuel gauge and the sending unit. A poor ground is frequently responsible for fuel gauge problems.
  • 4 Release the wire that connects to the fuel tank's sending unit. Confirm that there's no worn insulation that would permit wire contact to the body or frame. A fuel gauge reading of full generally indicates a problem with the tank unit, not the wiring.
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