P0461

CIRCUIT DESCRIPTION
The left fuel level sensor measures fuel level changes within the left fuel tank and changes resistance based on fuel level. The PCM monitors 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 tanks. This information is then sent to the IPC via the class 2 serial data circuit.

When the PCM senses a signal voltage lower than the normal operating range of the sensor, this DTC sets. The left tank fuel pump also supplies a small amount of pressurized fuel to the right fuel tank siphon jet pump through the auxiliary fuel feed rear 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 auxiliary fuel return rear 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 percent.

CONDITIONS FOR RUNNING THE DTC
The ignition is ON.

CONDITIONS FOR SETTING THE DTC
^ The primary fuel tank (left) is not full.
^ More than 241 km (150 mi) have been accumulated.
^ The PCM does not detect that the fuel level in the left fuel tank has not changed 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 mi). Observe, if the secondary fuel tank is empty, the primary fuel level should decrease after 241 km (150 mi).

ACTION TAKEN WHEN THE DTC SETS
^ The fuel gage defaults to empty.
^ The check gages indicator illuminates.
^ The PCM records the operating conditions at the time the diagnostic fails. The PCM stores the failure information in the Failure Records on the scan tool.

CONDITIONS FOR CLEARING THE DTC
^ The DTC becomes history when the conditions for setting the DTC are no longer present.
^ The history DTC clears after 40 malfunction free warm-up cycles.
^ The PCM receives the clear code command from the scan tool.

DIAGNOSTIC AIDS

IMPORTANT: When inspecting for a deformed or a warped fuel tank, measure the resistance of the suspect fuel level sensor at empty, with the sensor in the fuel tank, and again with the sensor removed from the fuel tank. The measured resistance values should be the same at empty. If the measured resistance values are not the same, refer to Fuel Tank Replacement (Right) or Fuel Tank Replacement (Left) in Computers and Controls Systems.

^ 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. Refer to Fuel Sender Assembly Replacement in Computers and Controls Systems. 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 gage displays empty.
- The check gage 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 the engine and idle for 5 minutes.
- Turn OFF the engine.
- Add the remainder of the fuel.
^ Test for an intermittent condition. Refer to Testing for Intermittent and Poor Connections in Diagnostic Aids.

The voltages in the Fuel Level Conversion Table are approximate values. Use this table to aid in diagnosis.

TEST DESCRIPTION

Steps 1-6:

Steps 7-12:

Steps 13-18:

Steps 19-29:

The numbers below refer to the step numbers on the diagnostic table.
7. 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.
10. 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.