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OBD-II Trouble Shooting Got a code reader? Find out what your GM car's Check Engine light is trying to tell you (and then turn Check Engine light off).

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Old 11-09-2009, 10:02 PM   #1
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Fuel Level Sensor Low Voltage

The fuel level sensor is a device used to determine the level of fuel in the tank. The PCM applies ignition voltage to the sensor. The sensor varies the voltage based on the level of fuel in the tank. The sensor resistance is high when the tank is full, and the PCM senses a high signal voltage. As the fuel level in the tank decreases, the sensor resistance drops, and the signal voltage at the PCM is pulled low. The PCM uses the fuel level input in order to run certain system tests. Some of these tests include:
EVAP system test
Misfire tests
Oxygen sensor tests
The PCM also sends the fuel level information via Class 2 serial data to the instrument panel cluster (IPC). The IPC uses the information to control the fuel gauge.
The PCM requires an accurate indication of fuel level for EVAP system diagnosis. The PCM monitors the fuel level sensor for signal voltage outside the normal range of the sensor. If the PCM detects a signal voltage less than the calibrated range of the sensor DTC P0462 will set.Symptoms
  • The PCM will not illuminate the malfunction indicator lamp (MIL).
  • The PCM will store the conditions, which were present when the DTC set as Failure Records Data only.
  • The ignition must be on.
  • The PCM detects a fuel level sensor voltage that is less then 0.4 volts for at least 10 seconds.
Check for the following conditions:
  • A faulty connection at the PCM – inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections.
  • Inspect the wiring harness for damage.
  • Turn off ignition, disconnect the fuel sender assembly connector. Turn on ignition (DO NOT START). Observer fuel gauge.
    • Does the gauge read full?
      • NO - Check the fuel level signal circuit for a short to chassis or ground. If problem found repair and re-test. If no problem found, replace the PCM
      • YES – Leave ignition on. Connect a jumper between the fuel level signal and the fuel level ground circuit in the harness connector. Does the gauge read empty?
        • YES – Replace fuel level sensor
        • NO – Check instrument cluster.
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