P0461

P0461-FUEL LEVEL SENSOR 1 PERFORMANCE





For complete wiring diagrams refer to Diagrams/Electrical.


Theory of Operation

The fuel level sending unit is attached to the side of the fuel pump module. The sending unit consists of a float, and arm and a variable resistor track (card). The fuel transfer lift pump is also attached to the fuel pump module. A constant input voltage source of battery voltage is supplied to the resistor track on the fuel gauge sending unit. This is fed directly from the ECM. NOTE: For diagnostic purposes, this 12-volt power source can only be verified with the circuit opened (fuel tank module electrical connector unplugged). With the connectors plugged, output voltages will vary from about 0.6 volts at FULL, to about 7.0 volts at EMPTY. The resistor track is used to vary the voltage (resistance) depending on fuel tank float level. As fuel level increases, the float and arm move up, which decreases voltage. As fuel level decreases, the float and arm move down which increases voltage. The varied voltage signal is returned back to the ECM through the sensor return circuit. Both of the electrical circuits between the fuel gauge sending unit and the ECM are hard-wired (not multi-plexed). After the voltage signal is sent from the resistor track, and back to the ECM, the ECM will interpret the resistance (voltage) data and send a message across the multi-plex bus circuits to the instrument panel cluster. Here it is translated into the appropriate fuel gauge level reading. When the fuel tank level is measured below 15%, the following fuel system monitors are shut off: P0191 (Fuel Pressure Idle Diagnostic portion of it), and DTC's P0300, P0301, P0302, P0303, P0304, P0305, P0306. The ECM will illuminate the MIL lamp immediately after this diagnostic runs and fails. The ECM will turn off the MIL lamp after the diagnostic runs and passes in 4 consecutive drive cycles.

- When Monitored:

While the engine is running.

- Set Condition:

Fuel level does not change by a calibrated amount over a calibrated amount of time.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test


1. EXTERNAL DAMAGE TO FUEL TANK

Visually inspect the fuel tank for external damage.

Is the fuel tank damaged from the outside?

Yes

- Fix or replace the fuel tank.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 2

2. FUEL LEVEL SENSOR

Disconnect the wiring harness from the fuel level sensor.


NOTE: Check connectors - Clean/repair as necessary.

Remove the fuel level sensor from the fuel tank.

Does the fuel level float move freely?

Yes

- Go To 3

No

- Replace the fuel level sensor.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

3. FUEL LEVEL SENSOR

Measure the resistance between the sensor (N4) signal circuit and (K900) return circuit while moving the sensor float arm.

Does the resistance level change as you move the sensor arm?

Yes

- Go To 4

No

- Replace the fuel level sensor.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

4. INSIDE OF FUEL TANK OBSTRUCTED DAMAGED

Visually inspect the inside of the fuel tank for obstructions.

Is the inside of the fuel tank damaged or obstructing the fuel level sensor?

Yes

- Test Complete.

No

- Replace the fuel tank.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test