I have a 2007 Chevy Tahoe and I have noticed over the past month that the gas gauge has grown a mind of it’s own… it will randomly move from Empty to Full, back to Half way, to Full and so on and so forth… I have heard that this might be a “Fuel Sending Unit” problem, but that would show a Check engine light… right??? Or it could be a faulty Gas cap??? Any suggestions? I can explain more if need be…
GM sending units seem to have a problem with sulfur contamination, the fuel gauge on my 2000 Blazer hasn’t worked in a couple of years. No check engine light. Try a bottle or two of Chevron Techron, it’s supposed to clean the sending unit. Techron didn’t work on my Blazer, but the truck ran a bit smoother.
" … I have heard that this might be a “Fuel Sending Unit” problem, . . ."
Yes, It Sounds Like That Is The Problem.
" . . . but that would show a Check engine light… right???
No, The Defective Gauge Does What You Have Described. The Check Engine Light Doesn’t Illuminate.
GM has had several model-years and several makes / models that have in-the-tank fuel sensors (sending units) that are literally eaten up by sulfur in the gasoline.
I replaced one in one of my cars myself and saw what happens. There are tiny little electrical “fingers” on the “wiper” portion of the sensor arm that is connected to the float. It wipes over a part of a small circuit board as the float moves with fuel level and sends a signal indicating the fuel level. Those little metal fingers dissolve and start making poor contact with the circuit board.
The bad news is that after proper diagnosis and confirmation that the sensor is bad, I do believe that the tank has to be lowered and the fuel pump module extracted in order to install the sensor.
The good news is that I believe your vehicle has available just the fuel level sensor as a replacement part from GM and the part is not extremely costly. Some vehicles make it necessary to replace the whole fuel pump module / fuel sensor assembly at a much higher cost.
My GM passenger car had a small access panel in the trunk and I was able to replace the sensor (mine was about $50) myself in my driveway. Anyhow check with your Chevy dealer and / or GMC to check on the sensor availability and price. I understand that because GM replaced many of these under warranty and therefore made the sensor available and at a fairly low cost to keep their warranty repair expenses lower.
Get it fixed, but keep the mechanic happy and let your fuel level get pretty low before going for replacement. Otherwise the tank will be heavy and have to be pumped out.
CSA
Yes, as noted, yet another mess that GM made and left with consumers. You can try the Techron which probably won’t work. Other than that you live with it or have the gas tank dropped to replace it ($$).