P0461

Circuit Description
The left Fuel Level sensor, mounted in the rear side of the left fuel tank, measures fuel level charges within the left fuel tank. The left Fuel Level Sensor changes resistance based on fuel level. The Fuel Level Sensor has a signal circuit and a ground circuit. The PCM applies a voltage (about 5.0 volts) on the signal circuit to the sensor. The PCM monitors changes in this voltage caused by changes in the resistance of the sensor to determine fuel level.
When the fuel tank is full, the sensor resistance is high, and the PCM senses high signal voltage. When the fuel tank is empty, the sensor resistance is low, and the PCM senses a low signal voltage.
The PCM uses inputs from the Fuel Level Sensor to calculate the total fuel remaining in the fuel tank(s). This information is then sent to the fuel gauge via the class 2 circuit.
When the PCM senses a signal voltage lower than the normal operating range of the sensor, this DTC sets.
The following is a description on how the fuel pump/system functions: An electric high pressure fuel pump attaches to the fuel sender assembly inside the left fuel tank. The in-tank fuel pump supplies pressurized fuel through an in pipe fuel filter/pressure regulator assembly to the fuel rail. The fuel pressure supplied by the in-tank fuel pump exceeds the fuel injectors required pressure. The pressure regulator, which is part of the fuel filter assembly, regulates the fuel pressure supplied to the fuel injectors. Excess fuel returns from the fuel filter/pressure regulator, through a separate fuel return pipe, to the left fuel tank. The fuel pump delivers a constant flow of fuel to the engine even during low fuel conditions and aggressive vehicle maneuvers. The PCM controls the electric fuel pump operation through a fuel pump relay.
The left tank fuel pump also supplies a small amount of pressurized fuel to the right fuel tank siphon jet pump through the fuel feed rear crossover pipe. The pressurized fuel creates a venturi action inside the siphon jet pump. The venturi action causes the fuel to be drawn out of the right fuel tank. Fuel is then transferred from the right fuel tank to the left fuel tank through the fuel sender fuel feed pipe. The fuel system is designed to maintain a greater level in the left fuel tank then in the right fuel tank when the electric fuel pump is operating. The fuel transfer rate from the left fuel tank to the right fuel tank is less than the transfer rate from the right fuel tank to the left fuel tank. Therefore, with the electric fuel pump operating, the left fuel tank level should be higher than the right fuel tank level.
The fuel level in the fuel tanks equalize when the following occur:
^ The electric fuel pump is not operating.
^ The fuel level is greater than 50%.

Conditions for Running the DTC
The engine is operating.

Conditions for Setting the DTC
^ The Primary fuel tank (left) is not full.
^ More than 241 km (150 miles) have been accumulated.
^ The PCM does not detect that the fuel level in the left fuel tank moved by at least 4.0 liters (1.1 gallons).

OR

^ The Primary fuel tank (left) is full.
^ The Secondary fuel tank (right) is near empty
^ The fuel level in both fuel tanks does not change after traveling more than 241 km (150 miles). Observe, if the secondary fuel tank is empty, the primary fuel level should decrease after 241 km (150 miles).

Action Taken When the DTC Sets
^ The PCM stores the DTC information into memory when the diagnostic runs and fails.
^ The Malfunction Indicator Lamp (MIL) will not illuminate.
^ The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.
^ The fuel gauge displays empty.
^ The Driver Information Center (DIC) displays a message.
^ The Check Gauge lamp illuminates.

Conditions for Clearing the MIL/DTC
^ A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
^ A last test failed (Current DTC) will clear when the diagnostic runs and does not fail.
^ Use a scan tool in order to clear the MIL/DTC.

Diagnostic Aids

Important:
^ Remove any debris from the PCM/TAC module connector surfaces before servicing the PCM/TAC module. Inspect the PCM/TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM/TAC modules.
^ For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter Kit J 35616-A. Using this kit prevents damage to the harness/component terminals.
^ The following may cause an intermittent:
- Poor connections
- Mis-routed harness.
- Rubbed through wire insulation.
- Broken wire inside the insulation.
^ Depending on the current fuel level, it may be difficult to locate a malfunctioning sending unit. The malfunction may only occur when the fuel level is full or near empty. The fuel sending unit may need to be removed for further diagnosis. A Fuel Level sensor that has an intermittent condition causes this DTC to set. Remove the Fuel Level sensor in order to test the resistance of the sensor. The resistance of the sensor should change from 40 to 250 ohms as the float arm is moved from the empty to full positions. Replace the sensor if the resistance did not change or is out of range.
^ The following occurs with this DTC set:
- The vehicle fuel gauge displays empty.
- The Check Gauge lamp illuminates.
- The Driver Information Center displays a message.
^ The PCM will not reset the mileage for this diagnostic if the fuel tanks are re-fueled to the same level as before the repair was made. Perform the following procedure in order to re-fuel the vehicle after replacing a sending unit or fuel tank:
- Add 25 percent of the fuel that you removed before the repair.
- Start and idle the engine for 5 minutes.
- Turn OFF the engine.
- Add the remainder of the fuel.
^ The voltages in the Fuel Level Conversion Table are approximate values. Use this table to aid in diagnosis.

^ Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed. For an intermittent, refer to Symptoms. Symptom Related Diagnostic Procedures

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. The PCM set DTCs P0461 and P1431 if one of the following conditions exists:
^ No fuel transfer between fuel tanks (i.e. Siphon Jet pump inoperative).
^ The left side Fuel Level sensor cannot obtain a predetermined upper threshold.
^ The right side Fuel Level sensor cannot obtain a predetermined lower threshold.
^ The left Fuel Level sensor is stuck in the full position.
3. This step determines if fuel is being transferred to the right fuel tank. The fuel pump runs for 2 seconds each time it is commanded ON with the scan tool. The fuel pump must be enabled several times to achieve the time specified in the diagnostic table.
4. This step determines if fuel is transferred to the left fuel tank. The fuel pump runs for 2 seconds each time it is commanded ON using the scan tool. The fuel pump must be enabled several times to achieve the time specified in the diagnostic table.
5. This step determines if a circuit condition is causing the fuel level signal to be at a fixed value.
6. This step determines if a circuit condition is causing the fuel level signal to be at a fixed value.
7. This step determines if a circuit condition is causing the fuel level signal to be at a fixed value.
8. This step determines if a circuit condition is causing the fuel level signal to be at a fixed value.
9. The fuel level information is important for diagnosis. The fuel level information can determine how much fuel is remaining. Also, review failure records to determine how many miles have been traveled since the DTC set. Inquire with the customer for fuel level information. Refer to Diagnostic Aids for fuel level conversion table. Ask the customer the following questions:
^ Has the vehicle just been re-fueled (full tank)
^ How many miles have been traveled since the last fill-up.
^ How many miles have been traveled since the LOW FUEL message appeared and the fuel gauge went to empty.
10. The voltages at 2.5 volts indicates that the PCM and wiring are OK. The Left Fuel Level sensor may be stuck within range (2.5V). The vehicle may need to be driven and retested before refueling, or fuel may be drained from the Left Tank as the Fuel Level Sensor voltage is monitored. If the Left Fuel Level sender is not stuck, the following could be what caused the DTCs to set:
^ The fuel tanks over filled.
^ Fuel level that is almost empty and then re-fueled with only a couple gallons.
^ The Fuel Level sender un-stuck while re-fueling.
^ The Fuel Level sender un-stuck on rough road or going around a corner.
12. Add the appropriate amount of fuel if the fuel level is below a half tank. Refer to Diagnostic Aids for fuel level conversion table. The values in this table are approximate values. You should be able to determine the fuel level even if there is a malfunctioning sensor. The fuel level information is Important. The fuel levels in each tank should equalize when the vehicle sets with the engine off for a couple of hours. The fuel level will not equalize as quick or at all if the fuel level is below 50%.
13. The fuel levels in each tank should equalize when the vehicle sets with the engine off for a couple of hours. The fuel level will not equalize as quick or at all if the fuel level is below 50%. It is Important that the fuel level is greater than 50% before performing the next step.
14. Starting the engine allows fuel to transfer to the left fuel tank. The fuel transfer is greater to the left fuel tank then to the right fuel tank while the engine is operating. The engine must be started after fuel is added. This step tests if fuel level voltages change when the fuel tanks are equalizing. Once the fuel tanks equalize, and the engine is started, the left fuel tank level should increase and the right fuel level should decrease.
15. The fuel level sensors are not stuck if the fuel level increased for the left fuel tank and decreased for the right fuel tank. The following could have caused the DTCs to set:
^ The fuel tanks over filled.
^ Fuel level that is almost empty and then re-fueled with only a couple gallons.
^ The Fuel Level sender un-stuck while re-fueling.
^ The Fuel Level sender un-stuck on rough road or going around a corner.
16. This step determines if fuel is transferred to the right fuel tank. The fuel pump runs for 2 seconds each time it is commanded ON with the scan tool. The fuel pump must be enabled several times to achieve the time specified in the diagnostic table.
17. This step determines if fuel is transferred to the left fuel tank. The fuel pump runs for 2 seconds each time it is commanded ON using the scan tool. The fuel pump must be enabled several times to achieve the time specified in the diagnostic table.
18. This step determines if a circuit condition is causing the fuel level signal to be at a fixed value.
19. This step determines if a circuit condition is causing the fuel level signal to be at a fixed value.
32. The PCM will not reset the mileage for this diagnostic if the fuel tanks are re-fueled to the same level as before the repair was made. Perform the following procedure in order to re-fuel the vehicle after replacing a sending unit or fuel tank.
1. Add 25 percent of the fuel that you removed before the repair.
2. Start and idle the engine for 5 minutes.
3. Turn OFF the engine.
4. Add the remainder of the fuel.