Fuel gauge issue?

BHAMDOC1973

MEMBER
2004 BUICK LESABRE
V6
2WD
AUTOMATIC
198,000 MILES

Noticed it was on empty with the warning light lit, then went to start it again and it showed full. Read online as it being a common issue with gauge step motor or the fuel tank leveling unit. How can I tell which it is? Everything else in the cluster works. Looked at the digital part of dash and it matches the gauge. While driving gauges fluctuate, all of a sudden goes to 1/2 and range reads 259 when all way on full reads 415 miles left. How can I determine if it's a fuel gauge issue or the leveling in tank? Not sure whether the needle controls the range or the digital tells the needle to move.

2 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,643 POSTS

The fact that the digital part of dash and it matches the gauge tells us the gauge is working correctly. This means the fuel level sender inside the tank is bad, which is common as well, but to be sure we should do a CAN scan to see what comes up. You can get a CAN scanner (Controller Area Network) from Amazon for about $36.00.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Amazon CAN scanner link for about $35.00.

https://amzn.to/3R9lJ60

Here is how to change the sender out in case you need it. Check out the images (below). Let us know what happens and please upload pictures or videos of the problem.

Images (Click to make bigger)