The powertrain control module (PCM) uses the fuel level input from the fuel level sensor in order to calculate the expected vapor pressures within the fuel system. The vapor pressures vary as the fuel level changes. The vapor pressure is critical to determining if the evaporative emission (EVAP) control system is operating properly. The fuel level information is used in determining whether to run an EVAP control system diagnostic. A fuel level that is too high or too low may prevent the EVAP control system diagnostics from accurately detecting a fault.

The ignition is On or the engine is running.

The scan tool will display a default value of 100 percent all the time when a Current fuel level sensor circuit DTC is present. Clear any current or stored fuel level sensor circuit DTCs before diagnosing the fuel level sensor circuit with a scan tool.

An open or a short to ignition voltage in the fuel level sensor circuit will indicate a 0 percent fuel level on the scan tool.

A short to ground in the fuel level sensor circuit will indicate a 100 percent fuel level on the scan tool.

Check the resistance of the fuel level sensor at the following positions:

Check for a faulty electrical connection at the PCM.

If DTC P0463 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool Clear DTC Information function. Road test the vehicle while monitoring the DTC P0463 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0463 appears in the Not Ran Since Code Cleared list, the P0463 diagnostic has not yet run. When the DTC P0463 does not appear in the Not Ran Since Code Cleared list, the P0463 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the P0463 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.

An intermittent malfunction may be caused by a problem in the fuel level sensor electrical circuit. Inspect the wiring harness and components for any of the following conditions:

If the DTC P0463 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC was first set.

The numbers below refer to the step numbers in the diagnostic table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step determines if the fault that set the DTC is still present.

3. This step checks for a faulty PCM. If the fuel gauge indicates the correct amount of fuel, there is a voltage fault within the PCM.

4. In order to locate the C401 connector, follow the fuel tank wire harness to the square pass-through grommet. The grommet is located in the frame rail below the left taillight assembly. Gently pull the grommet and harness out of the frame rail. The C401 connector is located a couple of inches from the pass-through grommet.