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Discussion Starter · #1 · (Edited)
I got an invalid FMM message tonight, which I delayed acting upon. What should I do? I've got 1.8 gallons in the tank right now (as per Voltstats), with the car's gas range only showing 68 miles on the android App.

I bought my car in Dec 2016, eight months ago, purchased with a full tank. I finished burning through that entire initial tank in the middle of May, about 3 months ago, on a road trip that included 675 gasoline miles. So clearly, my average fuel age is nowhere near 1 year old, and it should a bit over 3 months old. During the drive home, I had some engine warning light come on, and Chevrolet replaced the PCM (hybrid powertrain control module), so it is possible something got incorrectly reset at that point. I don't know. Anyway, since May I've burned through another 2.67 gallons of gas including one gallon last weekend, and the tank now has under 2 gallons.

So, I could delay the FMM 24 hours (tomorrow evening), in which case it would probably force itself to come on Monday morning on the way to work. Or I could top off the tank. Or I could let it do FMM on the 2 miles trip to the gas station, burning 0.05 gallons or so. I think I read somewhere on the forum that once you get one of these invalid FMM errors the car will never again use the battery again until you take it to the Service Center even if you fill up the tank. But I don't know. Any suggestions? Here is the thread I looked at but the Op never reported on what happenned: http://gm-volt.com/forum/showthread.php?238889-Fuel-Maintenance-Mode-Gen-2 BTW, it was a fuel maintenance mode message, not an engine maintenance mode message.

update I read in the manual, "... If No is selected, the FMM Request screen will appear when the vehicle is next started... If the FMM request was delayed for one day, FMM will start at the next vehicle start... After FMM has run it is recommended to fill the fuel tank.".

This sort of implies maybe you have to let FMM run before you top off the tank. Maybe just letting FMM run for 2 miles on the way to the gas station would be safer than adding gas while it still lets me delay FMM and run on battery...
- Sheldon
 

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Discussion Starter · #5 · (Edited)
Eventually the 24 hours ran out. I added 2 gallons of gas this morning, and the Volt switched back to EV mode. The fuel was not stale since I've burned through 20 gallons since the beginning of May 2017. Before the FMM kicked in, I had driven 96 electric miles Saturday and Sunday. But then I had to drive 4 miles using the ICE to pick up dinner; and then another mile this morning on the drive to the gas station. The Volt is back to normal now. As noted, there was a warning light that led to Onstar service after our road trip in May, so that's probably why the computer got confused.
 
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