what controls the Estimated milage on a tank of gas?

[BlueCollarTahoe]

how does the car estimate how many miles you have with whats in the tank? reason i ask is because an ODBII scanner i have says the ECU will say i have 150 miles left to empty or 46% full but the DIC screen will say 30 miles left. if i reverse it goes down. once i park the estimated miles left goes up. is there a sensor somewhere that controls this?

 

[zbad55]

The float level sensor in the tank is what controls the range left in the tank. When the float reads a certain ohm's the PCM reads ths and sends an average MPG to the DIC, this also triggers your low fuel light

 

[BlueCollarTahoe]

to replace that might as well replace the whole pump then no?

 

[M1Gunner]

Unfortunately, I’m gonna have to disagree with @zbad55 . Reason being is that the computer is calculating the level of fuel left in the tank to the speed of the vehicle. When idling the miles to empty should go down. On the highway however the longer you drive the more miles to empty will display. So if drive a full tank on the highway your distance will increase to say 325 miles with a full tank. Stop and go traffic driving with result in a much lower miles to empty reading.

 

[Scottydoggs]

sounds like the level sensor in the tank is moving as it should when the gas gets pushed one way or the other.

some how the mpg are calculated and then it does some math to est the miles left in the tank via how much is left in the tank. if the gas level drops the miles to empty will also drop.

 

[swathdiver]

On a flat and level surface at the filling station, my truck will take on 98% of rated capacity in fuel (supposedly). However, as soon as she hits the road and settles down at speed it reads 85-88%. Come to a light and goes back up to 98%. Once the tank was down to 11%. 50 miles later it was still at 11% but crossing a curved bridge it went to 3% on the ascent. It's a 32.2 gallon tank but have no recollection of ever filling it past 27.2 gallons with the idiot light on.

I would say the mileage stats are calculated like Carl and Jason said; the information is calculated in the ECM and sent to the IPC module.

 

[BlueCollarTahoe]

What are thr signs of a malfunctioning level sensor?

 

[Scottydoggs]

level senders dont work when they go bad. aka it lays on E and stays there no matter how much gas is in the tank.

the sender has to move, its a float. so if you go fast in reverse the gas will move to the front of the tank, making a wave even inside, the float has to deal with all that. so its gonna read up and down till the gas stops moving around.

 

[swathdiver]

What are thr signs of a malfunctioning level sensor?

The computer system tests for this and would throw a code. The truck and the scanner are likely using differing formulas.

My manual calculations are within tenths of a gallon and usually hundredths of a gallon compared with the truck's computer.

 

[BlueCollarTahoe]

thanks guys appreciate it. i got another thread i need some answers on lol