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Fuel Gauge Reading Incorrectly: What Went Wrong?

Fuel gauge reading incorrectly does not affect the engine functions or create any major problem. You can drive just fine without damaging any major component. But, not being able to read the correct gas level will result in running out of gas with no warning.

The functions of a fuel gauge are to show the amount of fuel in the gas tank and to give a warning when it’s time to refuel. Driving with a low level of fuel causes many long-term consequences like clogging the fuel pump, overheated engine, and premature wear of several engine parts.

Fuel Gauge Reading Incorrectly: What Went Wrong?

A vehicle’s gauge system comprises three basic parts: gauge, circuit, and sender. A fault in these parts will cause gauge failure or make it give incorrect readings. The four ways of how a fuel gauge can fail are:

1. Sending Unit Failure

The most common reason for a fuel gauge to not work. The gauge may read the voltage feedback from a dead sender as ‘Full’ or ‘Empty’.

incorrect fuel gauge reading
The fuel gauge won’t show the correct reading.

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The sending unit continuously moves and rubs on the variable resistor when you drive the car. The constant friction wears off the contacts, leading to its failure.

2. Problems with the Circuit

Depending on the source of the trouble, there could be a voltage problem in the fuel sender, causing the gauge to receive no voltage response from there. Interruption in the ground for either the gauge or the fuel sender might cause the issue too. Other reasons could be corrosion or loose connections at the fuel pump module.

3. Gas Gauge Failure

A less common but not outright impossible reason. It could happen when the internal circuit is defective, shorted, or open.

4. Non-Functioning Instrument Cluster

The least common of all causes and its repair is the most expensive. Most modern vehicles have a fully integrated circuit. So, when one part fails, the whole unit needs replacement.

How To Identify The Problems With A Fuel Gauge?

For amateurs, contacting a professional mechanic is the best option. But, if you have previous experience, it is easy to find out the issues with the fuel gauge reading incorrectly with these tools:

  • A digital multimeter (DMM)
  • An electrical wiring diagram (EWD)
  • Basic hand tools

Carry out these following tests to identify the problem source of fuel gauge reading incorrectly.

Instrument cluster self-test: The procedure involves doing a series of tasks including switching the headlight on, press on the odometer button, etc. The task sequence could be different for older vehicles. You need to check the owner’s manual to know the correct order.

fuel gauge reading incorrectly
Check the owner’s manual for the correct procedure.

Fuel sender test. Conduct the test when the tank is lower than half to avoid splashing hot oil. Use the multimeter to check for voltage on the pins, and it has to be 5 V or 12 V on one pin.

Gas gauge test. This inspection involves another voltage testing, and the reading has to be exactly the same as the fuel sender test.

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