Tank Mileage Reset

I'm about to turn 40,000 on my 2016 Taco and something happened the other day for the first time. Normally when I fill the tank I write on the gas receipt the tank mileage from the previous tank mileage indication (I periodically do the math and find the reading is very close). When you drive ahead a few feet, after filling the tank, the Tank Mileage indication resets to Zero. Well last week, when I pulled ahead, the gizmo did not reset !! Today I filled the tank and it did. Got me wondering what happened. My question for the 'Brain Trust' - What mechanism does this truck use to determine that the tank has been filed and it's time to reset this indication ?? I asked my dealer Service Adviser (whom I've worked with for man years) and he said he did not know - Who has figured this one out?

Thanks - Clay

 

I added a gallon or so from my dirt bike gas can and it reset my tank mileage. My guess is that when it detects more fuel than it had at it's last reading, it resets.

 

OK - But how does it do that - what kind of sensor is there in a tank that knows that it's been added to in order to resent the reading? ...This will help me understand why mine failed to reset.

 

It's your fuel gauge. The computer has code written that regularly asks itself if the amount of fuel has increased. When the answer is yes, it then resets the MPG for that tank.

 

That's reasonable - but what happened when it did not ? As I drove it - It continued to display what I though was close to the correct mileage for what I was doing. Computer glitch?

 

That's a darn good question. My guess would be that the query returned an error and did not process the answer. Now the computer is using the new amount of fuel and waiting for that amount to increase, which is why it reset on your next fuel up. Definitely weird for sure. If it doesn't happen again, I would say it was just a one-time error.

 

Maybe Toyota saw that contribution as a error . If it happens regularly then of my might be a sin 6th to

 

Any chance you didn't drive very far before refueling?

Despite the tank and filling neck holding up to ~23.7 gallons the fuel sensor does not read above 19.1 or 19.2... this is when the gauge starts moving off max. If you refuel before the gauge starts to move it will not reset.

 

Yesterday my 'Tank MPG' reset twice without filling up my truck. Anyone seen something similar happen?

It happened both leaving and returning to my driveway.

I'm at about 3/4 of a tank and back into my driveway, which has a 5 to 10 degree slope. If the reset is based on a fuel level sensor in the tank, it may well be that the slight grade, low speed, and some sloshing is confusing the software.

Still, took me by surprise to have an apparent glitch in a new truck. Hopefully it's due to sensor location and specific conditions, not real computer or firmware glitches.

 

that's my guess, i would start by disconnecting the battery for a few minutes and see if it happens again.