2006 2500 8.1L Suburban w/dual fuel tanks having gauge issue

randallcook · February 20, 2015

2006 2500 8.1L Suburban w/dual fuel tanks having gauge issue. Most prevalent on the upper end of the gauge, after driving around 30 miles, the gauge will visually drop about 1/8-1/4 tank worth and then visually raise back up again to near starting point. The Average Mileage Remaining also changes accordingly with the gauge fluctuation.

This is during driving on flat surfaces, without curves, embankments, hard braking, or erratic driving. So, it is not caused from fuel sloshing in the tanks. The gauge and "avg mileage remaining" changes way more than I believe it should for normal operation. What could it be?

Also, I've had two garages look at it. The first one swapped the ECM with no luck and replaced the sending units with no luck.

servantsalesmen · February 20, 2015

It's very common for this generation of trucks to have issues with the gauges not working. Mine have all crapped out on my 04 and 03. Just had the 03 cluster rebuilt for 110 bucks plus shipping. Also, just curious, what is the total fuel capacity of your truck?

00Silverado4x4 · February 21, 2015

Also could be having a fuel sending unit/wiring problem. I'd double check the sending unit & it's connections.

randallcook · February 21, 2015

It's very common for this generation of trucks to have issues with the gauges not working. Mine have all crapped out on my 04 and 03. Just had the 03 cluster rebuilt for 110 bucks plus shipping. Also, just curious, what is the total fuel capacity of your truck?

About 38 gallons total between the two tanks.

Also could be having a fuel sending unit/wiring problem. I'd double check the sending unit & it's connections.

The first service garage replaced the sending units. Would you still suspect faulty ones?

sdeeter19555 · February 21, 2015

I'd suspect wiring or a connection/connector between the sending unit and gauge cluster.

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Burbman · February 23, 2015

Had a similar problem on my 01 Suburban, the gauge would go flat to empty and the low fuel message would come on. Would happen intermittently and the gauge would come back on after a minute/day/week, was no rhyme or reason to it. Turned out to be the read sending unit. From what I have read, the truck has two tanks, each tank has it's own fuel pump and sending unit. The front pump runs full time to feed the engine, the rear pump gets turned on/off by the PCM under certain conditions, which I have not been able to find out what they are.

The PCM drives the gauge cluster, and it essentially takes the readings from both tanks and uses some kind of formula to determine what level to show on the gauge. My back sending unit was intermittent, and when the PCM couldn't get a reading on the back unit it would flatline the gauge at empty.

Surprised that you didn't have new fuel pumps put in when you had new sending units installed. That's a big labor bill to drop both tanks, and anything over 100K on the factory pumps is borrowed time. They also advise changing the wiring connectors when you change the pump, you may just have a loose or corroded connector(s). Unfortunately you need to drop the fuel tanks to get to the connectors....

I also changed my brake and fuel lines to stainless as part of that project, but the gauge works fine now.