fuel gauge not working, no code flashing

[spongebob]

full of fuel, gauge reads empty with a light saying its low.

This is a work truck with 330,000 miles, a ladder rack and tool boxes, hope i don't have to remove the bed.

thoughts

[rapidoxidationman]

A stuck float on the fuel level sender? Can you get to the wiring harness to do some electrical tests?

[spongebob]

I have a full load in the bed....so getting to the sending unit would be a last resort ( thanks GM for not putting a plate in the bed over the fuel tank sending unit)..

[Kennedy]

Not overly difficult to drop the tank. Lines, wiring, filler neck screws, ground strap, then 2 bolts.

[spongebob]

fuel sending unit is $350...I guess I should have one if Im going to lower the tank huh??
anything else I should get while Im in there?

[DmaxMaverick]

Before you get waist deep into this, be sure it is the sender, and not the gage or communication issue. Use a scanner to read the fuel % level. If it matches the gage, then it's likely the sender. If it doesn't, then it's more likely a gage (IPC) or harness issue.

[spongebob]

My tank is full, gauge reads empty and the light is on.

I have a CanOBD 2&1 scanner.

am I in the ball park?

My scanner it seems will only get a code, I have no code..what scanner do I need?

[DmaxMaverick]

You have a "code reader", not a scanner. A failed fuel level sender won't set a code. THE scanner is the Tech II, what your dealer and some shops use ($$). Other scanners, such as Snap-On, can do much the same. Other devices, including some power programmers (Predator, In-Tune, Hypertech, Edge) have system parameter scanning abilities, and many of them don't require it to be "married" to the truck just for scanning (borrow one from a friend with a similar truck). In all likelihood, the sender is the problem. However, replacing it is a lot of work, to just find out it isn't the problem.

[rapidoxidationman]

If I remember correctly, there is a way to send a voltage signal to the instrument cluster gauge and test it to see if it is actually sweeping properly. I don't know that exact technique, but I'm sure someone here does.

[Kennedy]

I believe that the sender sends the voltage to the ECM which then drives the gauge so there should be data to read and verify. If this was an early truck I would definitely suspect the cluster, but it seems that the later ones have been much more reliable. Still worth some digging.

[spongebob]

the 1st thing I noticed was when I filled the tank up, registered 3/4 full then dropped to empty and then went back up to almost full then back down to empty with the warning light lite, and a message saying Im low on fuel.

[Yukon6.2]

I just dropped the tank on a 03 that i just bought,not a horrible job.
But i have a hoist and a tranny jack.My tank was full so i siphoned out most the fuel.My truck was filty dirty and i couldn't wash it,that was the worst part of the job dealing with a dirty truck/tank.
In your case dropping the tank is the way to go,i had no choice my truck has a wrecker deck on it.

[spongebob]

thanks

[Kennedy]

FYI I just swapped the sending unit potentiometer part from a 2005 Dmax into my daughter's 2007 Impala. It seems that they are the same just different float arms. Plugs in up underneath and locks into the bucket same way. I just shortened the wires to match. I swept it on the car before I reinstalled and it worked, just need to get things finished and go fill up in increments to test it.

[spongebob]

thanks, Ill be going to O'Reillys tomorrow.

[Kennedy]

I would recommend OE only.

[spongebob]

I would recommend OE only.

too late, its on order...