04 yukon Denali stuck gas gauge :(

[John K86]

90k miles. Fuel pump replaced with AC-Delco. About 2 weeks later gas gauge was stuck on full after a full up. I tapped the tank with a rubber mallet and it fixed it so I just assumed I had a stuck float. 3 months later same problem. Gauge moves back and forth on start of but always showing full gas. Tapping tank didn't help. About a week later it dropped to empty and stayed stuck there with the light on. Mechanic dropped tank again and tried another new AC Delco pump. Says same issue. Told me it was the cluster. I replaced the stepper motors myself (tried 3 different ones on the Gas Guage) and still have the same issue so I'm assuming it's not the cluster. Looked at my mechanic bill and the receipt shows the part number for an XL 1500 version. I have the regular sized Yukon. So this got me Thinking they installed the wrong pump. Would it even fit? Would this cause the gauge error? Mechanic says car wouldn't start if it wasn't the right pump.

 

[John K86]

Image

 

[about20ninj45]

Regular Yukon's and denali xls have two different size tanks the xl has 32-33 gallon tank and Tahoe have a smaller one if I remember correctly. Not sure on pump size, but they probably are all the same unless you had a flex fuel vehicle, which in that case the pump is bigger and will fit the same size bucket.

If your mechanic has a scan gauge, tell him to hook it up and verify the fuel amount from the ecu vs the dash, so you can rule out the cluster. If that's the case, then he may have pinched or shorted a wire during install, that or either another bad float

 

[John K86]

Regular Yukon's and denali xls have two different size tanks the xl has 32-33 gallon tank and Tahoe have a smaller one if I remember correctly. Not sure on pump size, but they probably are all the same unless you had a flex fuel vehicle, which in that case the pump is bigger and will fit the same size bucket.

If your mechanic has a scan gauge, tell him to hook it up and verify the fuel amount from the ecu vs the dash, so you can rule out the cluster. If that's the case, then he may have pinched or shorted a wire during install, that or either another bad float

Going back today because he says he has another cluster we can try out in my vehicle. I sense the same
Results. I guess dropping the tank and inspecting the wiring is next

 

[about20ninj45]

He just doesn't want to drop the tank. He should have access to an obd2 scanner before you guys even go down that route

 

[John K86]

He just doesn't want to drop the tank. He should have access to an obd2 scanner before you guys even go down that route

Just left at shop now. They are going to do that scan first.
Thx

 

[John K86]

Just left at shop now. They are going to do that scan first.
Thx

The scan read that the error was in the control module and the error was between the communication of the radio and the cluster. I have an aftermarket Pioneer Radio/GPS that was installed prior to my purchase of the vehicle. They reset it and it cleared the code. Fuel gauge went back up to the correct reading. I was messing with the radio a few months back so perhaps wires were rubbing back there or pulled somehow (not sure, maybe a ground). I just pulled the radio out and wrapped anything exposed with electrical tape and tried to maneuver the screen back in trying to assure nothing woukd get squashed. Everything seems to be working now so I guess we will see if this was even the issue. The ironic part is that this happened once before but it was prior to me fooling with the radio.. and a tap on the gas tank had fixed it. Guess we will see what happens!

 

[John K86]

Yup... still not working!! It's pegged on Full. Drove 50 miles and hasn't dropped an ounce.
Any other ideas?

 

[about20ninj45]

Pull the fuse to the radio and see if that fixes your issue, I doubt it has anything to do with the radio

 

[retiredsparky]

You could go high tech on your troubleshooting if you can identify where the harness enters the cab, perhaps you can put a multimeter on the wiring to check the resistance reading of the gauge.As you use gas the resistance should change.