P0463

P0463-FUEL LEVEL SENSOR 1 CIRCUIT HIGH





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:

Ignition on and battery voltage above 10.4 volts.

- Set Condition:

The signal voltage from the sensor goes above a calibrated value for a calibrated amount of time.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test


1. FUEL LEVEL SENSOR

Disconnect the ECM harness connectors.

Disconnect the Fuel level sensor harness connector.


NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance of the Fuel level sensor across the (N4) signal circuit and (K900) return circuit.

Is the resistance less than 10 ohms?

Yes

- Go To 2

No

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

2. (N4) SIGNAL CIRCUIT SHORTED TO GROUND





Measure the resistance between the (N4) signal circuit in the sensor harness connector and battery negative.

Is the resistance less than 10 Ohms?

Yes

- Repair the (N4) signal circuit shorted to ground.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 3

3. ECM

Reconnect the ECM harness connector.

While monitoring with the scan tool, disconnect the Fuel level sensor harness connector.

Did the DTC P0462 set?

Yes

- Test Complete.

No

- Replace the ECM.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test