3.0 Duramax DEF gauge fluctuates a lot.

[jlong1984]

Is anybody else's DEF gauge all over the place? This morning it showed only two bars remaining but when I got back in the truck to drive home this afternoon it was 75% full. 

[Rocz3cqg]

I have not noticed the fluctuations but the DEF gage as you probably know it is not a true level or flotation sensor. I believe and I say believe that the sensor only informs the ECM that the DEF tank is Full and the ECM calculates usage and sends the corresponding signal to the digital level indicator. I was down 1 bar in the DEF gage, I added 1 gallon of DEF and the gage did not move for 2 weeks / 300 miles to indicate full.  Did it take the sensor getting uncovered to tell the system the DEF tank was full?

[newdude]

There is a delay in the DEF gauge which happens almost every time after filling the DEF tank.  Can take a few drive cycles to reset the level.  

 

From GM - Diesel Exhaust Fluid Consumption – TechLink (gm-techlink.com)

 

"Segmented DEF Level Gauge

The current 2020 Silverado 1500 and Sierra 1500 models have a DEF level gauge on the instrument cluster that provides drivers with a representation of how much DEF is in the DEF tank up. (Fig. 2) The DEF level gauge does not operate like a typical float-style gauge that is used in a fuel tank. The Engine Control Module (ECM) monitors the DEF level and consumption rate in order to calculate an estimated range. DEF levels are detected by the DEF level sensor.

 

There may be some fluctuation in the amount of DEF represented on the DEF level gauge. After filling the DEF tank, it may take a few key cycles to register the correct amount in the DEF tank. With the new segmented DEF level gauge, it is possible that after adding 5 gallons (18.9 L) of DEF that the gauge reads as a full tank after the fill event. However, if the actual level of DEF is just entering the last segment on the gauge, the gauge is likely to drop by one segment shortly after driving after the fill event. As a result, a driver could have an initial impression that the vehicle consumes an excessive amount of DEF."

Edited June 17, 2022 by newdude