FLSSensor

Fuel Level Sensor (FLS)

Group: Emissions and exhaust

The fuel level sensor (sending unit) reports how much fuel is left in the tank. Besides the dashboard gauge, the computer uses it to decide when to run the EVAP system test.

Contents

What does the FLS sensor do?

A float on an arm moves a wiper across a variable resistor. The resistance changes with the level and the instrument cluster (or the computer) turns it into the needle position or a percentage. The EVAP test only runs with the tank between roughly 15% and 85% full, which is why a faulty sending unit can set emissions codes.

Where is it located?

Inside the tank, built into the fuel pump module. Saddle tanks (on some rear-wheel-drive or 4x4 vehicles) have two sending units.

Signal type and reference values

  • Variable resistance. The ranges depend on the manufacturer; for example, about 10 ohms with a full tank and 180 ohms empty, or the other way around.
  • Some modern vehicles send the level over the CAN network from the fuel pump module.

Values are a guide only: always check the manufacturer's data for your engine.

Symptoms of a bad FLS sensor

  • The fuel gauge always reads full, always reads empty, or moves up and down.
  • The vehicle runs out of fuel while the gauge still shows fuel.
  • Codes P0460 to P0464 and, sometimes, incomplete EVAP tests.

How to test the FLS sensor step by step

  1. Note the reading, add a known amount of fuel and check whether the needle moves in proportion.
  2. Measure the sending unit resistance at the fuel pump module connector at several levels.
  3. Check the fuel pump module ground: a bad ground skews the reading.
  4. If the instrument cluster runs a gauge sweep self-test when you switch the ignition on, use it to rule out the gauge.

Trouble codes related to the FLS sensor

Frequently asked questions about the FLS sensor

Do I have to replace the fuel pump if the sending unit fails?
On many vehicles the sending unit is sold separately; on others it only comes with the complete module.
What does code P0463 mean?
That the fuel level signal is abnormally high, usually because of an open circuit or a stuck float.

Updated September 25, 2026. Values are a guide only: always confirm them in the service manual for your engine.

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