Perceived Scangauge inaccuracy - is it the gauge or vehicle?
 

I have an older version 3.17 ScanGauge II I recently started using in a 2008 Dodge Grand Caravan with the 3.3 liter flexfuel engine. I had used it with a Chevy Colorado many years ago and recently found it so I thought I'd start using it to help improve my driving habits. Not sure if this is normal... When watching the instant MPG readout, if I am coasting in gear at any speed over approximately 20mph, the numbers don't go to 100 or 999 or --- like they do with the factory instant readout in my 2017 Jetta 1.4t. They'll read no higher than about 60mpg. I'm curious if this is normal or if I could have a leaky injector, fuel pump issue, or something else.
I haven't had access to my Jetta to try the ScanGauge in that car.

Anyone?

So it will go to 999 when you're coasting below 20 MPH? What happens if you downshift while coasting?

I'd take a look at fuel consumption on the gauge. When a vehicle is in DFCO, it should show 0 gal/hr.

Did you also setup the gauge with the various parameters such as engine size, etc?

No, neither my VW factory instant MPG or my Dodge with the SG would read 100-999 mpg when coasting in gear below 20mph. I wouldn't expect them to at that speed.

I'll check GPH when in DFCO.

I setup the SG with engine size, units, etc...

There's a setting you can adjust in the SG to adjust DFCO detection. I don't remember what it's called though - check the manual.

There's no problem with your car as OBD gauges don't measure fuel at all, only air. When SG detects a closed TPS and pulling Timing Advance it 'assumes' DFCO, it doesn't actually 'know. Fine tuning is what that adjustment is for.

(In diesels it assumes DFCO at closed TPS and falling road speed - it never picked up DFCO at all in my VW TDI, but worked out of the box with Ford and Renault diesels.)

I've had my SG, UG and Torque Pro through several cars and there are almost always nuances in setting them up right that varies from vehicle to vehicle.

Thank you. I just watched my ScanGauge as I coasted to a stop from various speeds and at no point did the gallons per hour read under .44