Gas gauge isn't reading correctly

is there a way to reset the gas gauge on my 2013 Tacoma? .....it's not reading correctly & is about just an 1/8 of a tank off when i fill up (shows less)

 

Not that I have ever heard of, the gauge is operated by a potentiometer (sending unit).
It basically works by resistance, which controls the fuel gauge.

Most of the time, it’s the sending unit.
Rarely is it a resistance problem in the wiring in my experience.
However, there is a possibility it’s the wiring, or gauge it’s self.
TBH, I’ve never had to work on one on a Tacoma. And I’m not 100% sure what converts the signal on the Tacoma? The ecu or the gauge itself? Maybe someone else will know?

Most of my experience has been with GM trucks.

 

My vote is the sending unit.

 

https://auto.howstuffworks.com/fuel-gauge1.htm

Sending Unit

The sending unit is located in the fuel tank of the car. It consists of a float, usually made of foam, connected to a thin, metal rod. The end of the rod is mounted to a variable resistor. A resistor is an electrical device that resists the flow of electricity. The more resistance there is, the less current will flow. In a fuel tank, the variable resistor consists of a strip of resistive material connected on one side to the ground. A wiper connected to the gauge slides along this strip of material, conducting the current from the gauge to the resistor. If the wiper is close to the grounded side of the strip, there is less resistive material in the path of the current, so the resistance is small. If the wiper is at the other end of the strip, there is more resistive material in the current's path, so the resistance is large.

In the sending unit, the fuel has to drop below a certain level before the float starts to drop.
When the float is near the top of the tank, the wiper on the variable resistor rests close to the grounded (negative) side, which means that the resistance is small and a relatively large amount of current passes through the sending unit back to the fuel gauge. As the level in the tank drops, the float sinks, the wiper moves, the resistance increases and the amount of current sent back to the gauge decreases.

This mechanism is one reason for the inaccuracy of fuel gauges. You may have noticed how your gauge tends to stay on full for quite a while after filling up. When your tank is full, the float is at its maximum raised position -- its upward movement is limited either by the rod it's connected to or by the top of the tank. This means that the float is submerged, and it won't start to sink until the fuel level drops to almost the bottom of the float. The needle on the gauge won't start to move until the float starts to sink.

Something similar can happen when the float nears the bottom of the tank. Often, the range of motion does not extend to the very bottom, so the float can reach the bottom of its travel while there is still fuel in the tank. This is why, on most cars, the needle goes below empty and eventually stops moving while there is still gas left in the tank.

Microprocessor-controlled Gauges

Some newer cars have a microprocessor that reads the variable resistor in the tank and communicates that reading to another microprocessor in the dashboard. Carmakers can tinker with the gauge movement a little -- they can compensate for the shape of the tank by comparing the float position to a calibration curve. This curve correlates the position of the float with the volume of fuel left in the tank. This allows the gauge to read more accurately, especially in cars with complicated gas-tank shapes.

Systems like this can also trigger a fuel light that signals when fuel is getting low. Most of these lights come on while there are still a couple of gallons of gas left in the tank, giving you plenty of time to stop for fuel.

The microprocessor can also provide some damping to the needle movement. When you go around a turn, or up a hill, the fuel can slosh to one side of the tank and quickly change the float position. If the needle were to respond quickly to all of these changes, it would be bouncing all over the place. Instead, software calculates a moving average of the last several readings of the float position. This means that changes in needle position occur more slowly. You may have noticed this when filling up your car -- you'll finish filling the tank long before the needle reaches full.

While fuel gauges are far from exact, they err on the conservative side.

 

^^^ sounds like i have an issue with the sending unit.........it all started when i filled up on a -15 degree day......not changing out the sending unit at this time, so i'll just have to live with it being about an 1/8 of a tank shy.....thanks for the input/info guys

 

I agree. Not a big deal as long as you're not in the habit of running to the empty mark like my wife... I would also use a trip meter to track mileage between fill ups.

 

Has anyone else had this issue? Just today I filled up completely to the top and my gauge only read 7/8. Truck is a 2022 with less than 2000miles.

 

Most reports are of the DTE being off.
Did you DTE go back up to normal range?

The gauge operates off a potentiometer.
The cluster is getting a reading from the sending unit in the tank.

I’d personally fill it back up at 1/2 tank and see if the problem resolves on its own.
If not, take it in for warranty. I would not touch it, let Toyota “fix it”.

 

I've never looked at the DTE so can't comment on that. I was talking about the gas gauge/level needle. I'll check it on next fill-up. Maybe just a fluke.