P0463 Fuel Level Sensor Circuit Signal High/Open trouble code. In this video I will show you how to test a fuel tank sending unit (float). Typically the spring loaded fingers that ride on the resistor in the tank will break off, ruining the sending unit. The only fix is to replace the float as an assembly or try to piece a new resistor assembly into the existing sending unit. The electrical design of the fuel tank sending unit that GM uses is identical in operation and testing as a temperature sensor. The difference is in what changes the resistance of the external resistor. On a temp sensor, it is temperature, on a fuel level sensor, it is the position of the float. For this reason, I have placed this video in my Section 6 "Thermistors" playlist.

Engine Performance Diagnostics chapter 6 pages 10-11

symptoms 50

  • in-op fuel gauge
  • fuel gauge stuck on full or empty
  • fuel gauge works some of the time
  • trouble code P0463

fix 50

  • replace fuel tank sending unit

test shown enh 50

  • description and operation of the electrical circuit
  • fuel tank level signal and ground wire tests
  • how to perform a circuit integrity test

Tools used

  • scan tool
  • digital multimeter
  • back-probing tools

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(Chapter 6) Temperature Sensor, Thermistor Circuit Tests

Related videos:

How to test a coolant temperature sensor (ECT sensor test):


How to test an Engine Coolant or Intake Air Temperature Sensor (any car) :


What's on ScannerDanner Premium? ("Chapter 6: Thermistors" Preview) :


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For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available as an eBook or paper book.

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