Anyone who owns a vehicle knows a few basic parts of the car. You don’t have to be a mechanic to understand the basics of steering, braking and acceleration. The gas gauge is one of the parts that novice mechanics are most familiar with. That is because most of us spend a lot of time checking it to make sure the car isn’t going to run out of gas any time soon!
Like any other component in your vehicle, the gas gauge can break or suffer from electrical glitches that cause the meter to malfunction and display inaccurate information. This issue can be inconvenient and stressful if you don’t make the effort to keep your car’s gas tank full.
When a gas meter malfunctions, it could be for one of two reasons:
- The instrument cluster needs to be reset
- There is a mechanical or electrical failure in you fuses, wiring, instrument cluster, or sending unit that will require repair
Why Do Gas Meters Need To Be Reset
A gas meter may need to be reset for a variety of reasons. Typically it is just when the gauge is glitching which is usually a one time issue. In some cases there can be electrical issues with the system causing it to glitch. Resetting the gauge may help at the time, but you’ll likely continue to see the issue until you fix the larger problem with the system.
If you are interested in diagnosing issues with your fuel gauge, check out the further on in this article for more info.
How To Reset A Gas Meter
While some gas meters have an analog display and others have a liquid crystal one, they all do the same job. A gas gauge on a vehicle is intended to tell the driver how much gas the car has. In some cases vehicles will also have a display that tells the driver how many miles until empty (and personally I’ve had one act up and not the other at times).
Whether the malfunction is related to software, electrical or mechanical, when your fuel gauge isn’t working it can cause drivers a lot of anxiety when they don’t know how much fuel is actually in their tank. You may simply be experiencing a glitch in your system or you may have a more serious problem that needs fixing.
You can try to reset you system and see if this fixes your issue. Every make and model of vehicle will have their own specific instructions on how to do this which you can find in the owner’s handbook for the car. However, most vehicles have largely the same procedures for this.
- Park the vehicle on a level surface.
- Turn the ignition switch to the “On” position.
- Place the odometer display into the “ODO” mode.
- Turn off the ignition switch.
- Depress and hold the “ODO/TRIP” button while turning the ignition switch to the “On” position. Hold the ODO button for two seconds.
- Release and press the ODO button three more times within five seconds: Release-Press-Release-Press-Release-Press and Hold. Continue to hold the ODO button for at least five seconds until the leveling information is displayed on the odometer.
- Release the button.
- Depress and hold the “ODO/TRIP” button until the odometer display confirms that reset has begun (odometer reads “1”).
- Once reset is complete, the odometer returns to normal.
- Release the button.
- Turn off the ignition.
How A Gas Meter Works
The fuel gauge system effectively functions like the floater inside a toilet’s water tank. As the tank is filled, the floater rises with the gas level signaling to the vehicle that you have a full tank of gas. As the tank is emptied and the gas is used, the floater will lower and the system will display to the driver that there is less fuel. This is why your car can have an inaccurate reading if it is parked on a hill. That’s a basic definition. If you want more detailed information keep reading.
The float is made of a buoyant composite foam which is connected to a thin metal arm which connects to the variable resistor. The variable resistor is an electrical device that resists the flow of electricity and has the ability to adjust how much resistance it gives.
As you use the fuel in your vehicle the fuel level in your tank drops and the float drops with it. A sensor indicates the distance the float is sitting from the top of the tank triggering a variable resistor to change the electrical current resistance which in turn makes your gauge give you an accurate reading of how much gas is in your tank.
When your gauge is stuck on Full or Empty or just changing erratically, you know there is a fuel instrument problem.
Signs That You Have A Bad Fuel Gauge
- Erratic needle movement
- Tank reading E after just filling up or F when you haven’t filled up in a while
If your fuel sensor needle moves erratically or more quickly than you feel you are burning fuel this is likely indicative of an issue in your fuel gauge system.
Alternatively the gauge may read F and E all the time regardless of how much fuel you actually have. In some cases the fuel gauge will randomly read E and this can be fixed simply by turning your car on and then back on. This is likely caused by a wiring or sending unit issue.
What Causes The Fuel Gauge Not To Work?
There are 4 main components of the fuel gauge system that may cause the reading to be wrong. Any one of them could be causing your issue. They are fuses, gauge malfunction, sending system and wiring.
Most commonly it is the sending unit that is causing your gauge to show an inaccurate reading. This component reads the fuel tank level and sends the reading to the gauge.
Issues can also stem from blown fuses, or corroded wiring. You can self-test all of these parts at home with a few tools. If you’re interested in doing this check out the detailed step by step guide at the end of this article.
How To Tell How Much Gas You Have With A Bad Fuel Sensor
Drivers of vehicles with broken fuel gauges often suffer from anxiety and fear of being stranded due to running out of fuel, luckily there are a few ways you can ease this anxiety before you ever get the car fixed.
- Use your odometer and fuel efficiency to calculate how many miles you have left on average
- Fill up the car prematurely and often
- Utilize your cars miles to empty feature if it has one
Check Your Owners Manual
You can find the size of your gas tank located in your owner’s manual. Typically the average car has a range of 300- 400 miles and the fuel tank will hold between 12 and 20 gallons of fuel.
By estimating your vehicle’s fuel efficiency you can determine at approximately what odometer reading you will next need to fill up. Be on the conservative side of this range and I don’t recommend letting it get to the almost empty mark or you could find yourself stuck on the side of the road waiting potentially a couple hours for roadside assistance or walking down the highway to the nearest gas station to buy a portable gas tank.
Self Diagnosing Your Fuel Gauge Problem
There is usually a way to run diagnostics on your vehicle yourself. If your vehicle was made in the last 20 years, you can check your owner’s manual for the instrument cluster self test procedure and follow it to see if the cluster can be reset.
As we discussed earlier, this will involve holding the odometer down as you start the car or some other series of steps. The process is used to test the instrument panel gauges and lights. The fuel gauge should go up and down all the way during the test. If the fuel gauge needle doesn’t move, then you know you have an issue with the gauge itself. If not move onto the next check, fuses.
Fuses
Your car has two fuse boxes, one under the steering column in the interior of your car and one under the hood. Check your owner’s manual to determine where the fuse is located for the gas gauge. Once located open the fuel box and check all the fuses inside. If any are damaged or completely broken, replace them. If this doesn’t seem to be an issue, you’re going to move onto the next check, the sending unit.
Sending Unit
As we discussed earlier, sending unit issues is the most common cause of fuel gauge malfunctions. This component physically measures the quantity of fuel and then communicates the levels with the gauge in the dashboard.
Go and top off your car for this one because you’ll need a full tank to test the sending unit properly. You’ll also need a tool called a multimeter to test the resistance. Finally, you’ll need to know what the standard resistance is for the make and model of your vehicle. You can find this in the repair manual for your car.
After you’ve received your resistance results, compare them to the standard for your vehicle. If the resistance is even a few ohms off you’ll know that it is your sending unit that is causing you issues. In some cases all you need to fix this issue is a bottle of fuel system cleaner which will run you about $10. While there is a chance that this won’t fix your issue, about 25% of the time it does.
In these cases corrosion is keeping the float of the sending unit from doing its job properly and a thorough scrubbing from a fuel system cleaner will get it back to proper working conditions. If this doesn’t work you can remove and replace this part yourself or have your car sent out for repairs at the mechanic.
Gauges
The next cause can be as simple as a voltage issue in the gauge of the car. Follow your repair manual in steps to remove the instrument cluster in your vehicle. Use the multimeter to test the gauge which should come back as 12V. If the voltage looks good, then you likely have a faulty gauge that will just need replacing. A part can be ordered for this repair online.
Wiring
If all of these tests go according to plan and you still are unsure of the issue, the answer is likely the wiring and grounding. A common cause is wire corrosion especially in vehicles that have been exposed to water damage. You’ll want to thoroughly inspect the wire running from your fuel tank to the gauge, cleaning or replacing if necessary.
If you’re still unsure after your self diagnoses you should take your car to the mechanic to have a professional work on it.
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