GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Corvette 🢒 Body and Accessories 🢒 Instrument Panel, Gauges, and Console 🢒 DTC P0461

DTC P0461 WithoutFFS

Circuit Description

The left fuel level sensor measures fuel level changes within the left fuel tank and changes resistance based on fuel level. The PCMmonitors 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 feedrear pipe. The pressurized fuel creates a venturi action inside the siphon jet pump. The venturi actioncauses the fuel to be drawn out of the rightfuel tank.Fuel is then transferred from the right fuel tankto the left fuel tank throughthe auxiliary fuelreturn rear pipe. The fuel system is designed to maintain a greater level in theleftfuel tankthenin the right fuel tankwhen the electricfuelpump is operating. The fuel transfer ratefrom theleft fueltank to the rightfuel tankis lessthan thetransfer rate from the right fuel tank to the left fueltank. Therefore,with the electric fuel pump operating, the left fuel tank levelshould be higher than the right fueltanklevel.

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 levelshould 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 in Engine Controls.

    • 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 anintermittentcondition causes this DTC to set. Remove the fuel level sensorin order to test the resistance of thesensor. Refer to Fuel Sender Assembly Replacement inEngine Controls.The resistanceof the sensor should change from 40 to 250 ohms as thefloatarm is moved from the emptytofull positions. Replacethe sensor ifthe resistance did not change orisout 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 replacinga sending unit orfueltank:
       - 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 Conditions and Poor Connections in Wiring Systems.

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

Test Description

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

  1. This step determines if fuel is being transferred to the right fuel tank.

    The fuel pump runsfor 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.

    2.

  2. This step determines if fuel is transferred to the left fuel tank.

    The fuel pump runs for 2 seconds each time it iscommanded ON using the scan tool. The fuel pump must be enabled several times to achieve the time specified in the diagnostic table.

Step

Action

Values

Yes

No

Schematic Reference: Instrument Cluster Schematics

1

Did you perform the IPC Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

2
  1. Install a scan tool.
  2. Turn the ignition ON, with the engine OFF.
  3. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  4. Disconnect the left fuel level sensor.
  5. Connect a fused jumper between the left fuel level sensor signal circuit and a known good ground.
  6. Monitor the left fuel level sensor voltage using a scan tool.
  7. With the scan tool, observe the Fuel Level Left Tank in the PCM EVAP data list.

Is the voltage at the specified value?

0.0 V

Go to Step 3

Go to Step 22

3
  1. Connect a fused jumper between the left fuel sensor signal circuit and the low reference circuit of the left fuel level sensor.
  2. Monitor the left fuel level sensor voltage using a scan tool.

Is the voltage at the specified voltage?

0.0 V

Go to Step 4

Go to Step 21

4

Is DTC P1431 also set?

--

Go to Step 5

Go to Step 13

5

  1. Disconnect the right fuel level sensor.
  2. Connect a fused jumper between the right fuel level sensor signal circuit and a known good ground.
  3. Monitor the right fuel level sensor voltage using a scan tool.

Is the voltage near the specified voltage?

0.0 V

Go to Step 6

Go to Step 23

6
  1. Connect a fused jumper between the right fuel sensor signal circuit and the low reference circuit of the right fuel level sensor.
  2. Monitor the right fuel level sensor voltage using a scan tool.

Is the voltage near the specified voltage?

0.0 V

Go to Step 7

Go to Step 24

7

  1. Reconnect both fuel level sensors.
  2. Disconnect the auxiliary fuel feed rear pipe that connects the left tank to the jet pump from the right fuel tank sending unit.
  3. Insert the auxiliary fuel feed rear pipe into an approved gasoline container.

    4. Important: The scan tool will have to be commanded ON several times in order to achieve the time specified.

  4. Command the fuel pump ON for 10 seconds using the scantool.
  5. Measure the volume of fuel.

Is the volume of fuel greater than the specified value?

300 ml (0.633 pt)

Go to Step 8

Go to Step 20

8

  1. Reconnect the auxiliary fuel feed rear pipe to the right tank.
  2. Drain the left fuel tank until the left fuel sender voltage is between 1.0 V and 1.25 V. Referto Fuel Tank Draining in Engine Controls.
  3. Disconnect the auxiliary fuel return rear pipe that connects the jet pump to the left fuel tank sending unit.
  4. Insert the auxiliary fuel return rear pipe into an approved gasoline container.

    5. Important: The scan tool will have to be commanded ON several times in order to achieve the time specified.

  5. Command the fuel pump ON for 8 seconds using the scantool.
  6. Measure the volume of fuel.

Is the volume of fuel greater than the specified value?

332.6 ml (0.703 pt)

Go to Step 9

Go to Step 21

9

Reconnect the auxiliary fuel return rear pipe that connects the jet pump to the left tank

Was the vehicle just re-fueled to a Full tank,ask the customer?

--

Go to Step 10

Go to Step 11

10

Turn ON the ignition, with the engine OFF.

Are both the fuel level sensor voltages near the specified voltage?

2.5 V

Go to Diagnostic Aids

Go to Step 19

11
  1. Turn OFF the ignition.
  2. Add the appropriate amount of fuel to reach a fuel level of at least 50%.
  3. Start the engine and idle for ten minutes.
  4. Allow the vehicle to sit with the engine OFF for the specified time.
  5. Monitor the fuel level sensor voltages for both fuel tanks.

    6. Important: Observe and record both fuel level sensor voltages.

  6. Start the engine and idle for ten minutes.
  7. Compare voltages to previous recorded voltages.

Did the Fuel Level sensor voltage for the left tank increase?

2 Hours

Go to Step 12

Go to Step 27

12

Did the fuel level sensor voltage for the right tank decrease?

--

Go to Diagnostic Aids

Go to Step 29

13
  1. Disconnect the auxiliary fuel feed rear pipe that connects the left tank to the jet pump from the right fuel tank sending unit.
  2. Insert the auxiliary fuel feed rear pipe into an approved gasoline container.

    3. Important: The scan tool will have to be commanded ON several times in order to achieve the time specified.

  3. Command the fuel pump ON for the specified time using the scantool.
  4. Measure the volume of fuel.

Is the volume of fuel greater than the specified value?

10 seconds 300 ml (0.633 pt)

Go to Step 14

Go to Step 19

14
  1. Reconnect the auxiliary fuel feed rear pipe to the right tank.
  2. Observe the left fuel level sender voltage with a scan tool.

Is the left fuel level sender voltage above the specified value?

1.25 V

Go to Step 15

Go to Step 16

15

Drain the left fuel tank until the left fuel sender voltage is within the specifiedrange. Referto Fuel Tank Draining in Engine Controls.

Did you complete the action?

1.0-1.25 V

Go to Step 17

--

16
  1. Disconnect the auxiliary fuel return rear pipe that connects the jet pump to the left fuel tank sending unit.
  2. Insert the auxiliary fuel return rear pipe into an approved gasoline container.

    3. Important: The scan tool will have to be commanded ON several times in order to achieve the time specified.

  3. Command the fuel pump ON for the specified time using the scantool.
  4. Measure the volume of fuel.

Is the volume of fuel greater than the specified value?

8 seconds 332.6 ml (0.703 pt)

Go to Step 17

Go to Step 27

17
  1. Turn OFF the ignition.
  2. Remove the left fuel tank sender assembly. Refer to Fuel Sender Assembly Replacement in Engine Controls.
  3. Inspect the left fuel tank sender assembly for the following:
    4. • A stuck fuel level sender (i.e., the fuel strainer interfering with the sender float arm or fuel pump body)
    • Foreign material (ice)
  4. If you find a condition, repair the condition as necessary.

Did you find and correct the condition?

--

Go to Step 29

Go to Step 18

18

Replace the fuel sender assembly that did not measure near the specified value. Refer to Fuel Sender Assembly Replacement in Engine Controls.

Did you complete the replacement?

--

Go to Step 29

--

19

Repair the fuel lines between the fuel tanks for the following conditions:

    • Restrictions
    • Kinked line
    • Proper connections
    • Proper routing

Did you complete the repair?

--

Go to Step 29

--

20

Visually/physically inspect the fuel lines between the fuel tanks for the following conditions:

    • Restrictions
    • Kinked lines
    • Proper connections
    • Proper routing

Did you find and correct the condition?

--

Go to Step 29

Go to Step 28

21

Test the left tank fuel level sensor signal circuit for an open, for a short to ground, or for a high resistance. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 29

Go to Step 27

22

Test the left tank fuel level sensor ground circuit for an open or for a high resistance. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 29

Go to Step 27

23

Test the right tank fuel level sensor signal circuit and ground circuit for a high resistance, for a short to ground, or for a short to voltage.Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 29

Go to Step 25

24

Repair the open of the high resistance in the low reference circuit of the fuel level sensor circuit.

Did you complete the repair?

--

Go to Step 29

--

25

Inspect for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 29

Go to Step 26

26

Important: Program the replacement PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls.

Did you complete the replacement?

--

Go to Step 29

--

27

Replace the left tank fuel level sensor. Refer to Fuel Sender Assembly Replacement in Engine Controls.

Did you complete the replacement?

--

Go to Step 29

--

28

Replace the right tank fuel level sensor. Refer to Fuel Sender Assembly Replacement in Engine Controls.

Did you complete the replacement?

--

Go to Step 29

--

29
  1. Use the scan tool in order to clear the DTC's.
  2. Operate the vehicle within the conditions for running the DTC.

Does the DTC reset?

--

Go to Step 2

--