P0461

Diagnostic Chart 1 Of 2:

Diagnostic Chart 2 Of 2:

Fuel Level Sensor Inspection:

schematic:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) uses the input from the fuel level sensor in order to calculate the expected vapor pressures within the fuel system. Vapor pressures vary as the fuel level changes. Vapor pressure is critical to determining if the EVAP control system is operating correctly. 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.

CONDITIONS FOR SETTING THE DTC
The change in fuel level from the maximum to the minimum is less than 1 gallon, although the volume of the intake air is calculated at more than 660 kg.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) after two consecutive ignition cycles in which the diagnostic runs with the fault active.
^ The PCM records the operating conditions at the time that the diagnostic fails. This information is stored in the Freeze Frame buffer.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The MIL will turn OFF after 3 consecutive passing trips without a fault present.
^ A History DTC will clear after 40 consecutive warm-up cycles without a fault.
^ DTCs can be cleared by using a scan tool or by disconnecting the PCM battery feed.

DIAGNOSTIC AIDS
Check for any of the following conditions:
^ If DTC P0463 is also displayed, diagnose that DTC.
^ A stuck fuel level sensor may cause DTC P0461 to set.
^ A loose fuel tank baffle that may interfere with the movement of the fuel level sensor float.
^ A corroded chassis ground or a loose sensor chassis ground. Operate the tail lamps and the brake lamps while checking the fuel level sensor reading on a scan tool. Increasing the current flow through the G400 chassis ground can expose a faulty circuit connection.
^ A faulty electrical connection at the PCM.

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

An open in the fuel level sensor circuit will cause an empty fuel tank indication. A short to ground in the fuel level sensor circuit will cause a full fuel tank indication.

An intermittent malfunction may be caused by a fault in the electrical circuit of the fuel level sensor Inspect the wiring harness and the components for any of the following conditions:
^ Backed out terminals
^ Incorrect mating of terminals
^ Broken electrical connector locks
^ Incorrectly formed terminals or damaged terminals
^ Faulty terminal-to-wire connections
^ Physical damage to the wiring harness
^ A broken wire inside the insulation
^ Corrosion of electrical connections, of splices, or of terminals

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

TEST DESCRIPTION
The numbers below refer to the step numbers in the Diagnostic Table.
1. The Powertrain OBD System Check prompts the technician to complete basic checks, and to store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data that was taken when the fault occurred. The information is stored in the scan tool for later reference.
5. This step checks the circuit from the fuel level sensor to the PCM. Because the scan tool will display a default value of 100 percent if a fuel level sensor DTC is present. Before reading the fuel level with the scan tool, clear the fuel level sensor DTCs.
6. This step checks for a faulty fuel level sensor.