GM Service Manual Online
For 1990-2009 cars only

Object Number: 604192  Size: MF
Engine Controls Component Views
Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The fuel level sensor is device used to determine the level of fuel in the tank. The PCM applies an ignition voltage to the sensor. The sensor varies the voltage based on the level of fuel in tank. The sensor resistance is high when the tank is full, and the PCM senses a high signal voltage. As the fuel level in the tank decreases, the sensor resistance drops, and the signal voltage at the PCM is pulled low. The PCM uses the fuel level input run certain system tests. Some of these system tests include the following:

    • EVAP system
    • Misfire
    • Oxygen sensor

The PCM also sends the fuel level information via class 2 serial data to the IPC. The IPC uses the information to control the fuel gauge.

The PCM requires an accurate indication of fuel level for EVAP system diagnosis. The fuel level in the fuel tank changes the rate of vacuum decay for the EVAP system leak DTCs.

The PCM monitors the fuel level sensor for signal voltages outside the normal range of the sensor. If the PCM detects a signal voltage above the calibrated range of the sensor, DTC P0463 will set.

Conditions for Running the DTC

    • The ignition is ON.
    • System voltage is between 11 and 16 volts.

Conditions for Setting the DTC

The PCM detects a fuel level sensor voltage that is more than 3 volts for at least 10 seconds.

Action Taken When the DTC Sets

    • The PCM will not illuminate the malfunction indicator lamp (MIL).
    • The PCM will store the conditions present when the DTC set as Failure Records data only.

Conditions for Clearing the MIL/DTC

    • The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
    • The DTC can be cleared by using the scan tool Clear DTC Information function.

Diagnostic Aids

Important: Fuel level is used to determine EVAP system diagnosis. Always diagnose the fuel level sensor before any other EVAP system components or DTCs.

For additional diagnostic information, refer to Diagnostic System Check - Instrument Cluster in Instrument Panel, Gauges, and Console.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may assist in diagnosing the condition. The information may help determine how often the condition that set the DTC occurs.

Step

Action

Values

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Are there any Instrument Panel Cluster (IPC) DTCs set?

--

Diagnose the IPC DTCs first

Go to Step 3

3

  1. Turn OFF the ignition switch.
  2. Disconnect the fuel sender assembly connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the fuel level gauge.

Does the fuel level gauge indicate FULL?

--

Go to Step 4

Go to Step 5

4

  1. Leave the ignition switch ON.
  2. Connect the appropriate jumper between the fuel level signal and the fuel level ground circuits in the harness connector.
  3. Observe the fuel gauge.

Does the fuel gauge indicate EMPTY?

--

Go to Step 6

Go to Diagnostic System Check - Instrument Cluster

5

  1. Check the fuel level signal circuit for a short to chassis or the fuel level sensor ground.
  2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 8

Go to Step 7

6

Replace the fuel level sensor. Refer to Fuel Level Sensor Replacement .

Is action complete?

--

Go to Step 8

--

7

Important: The replacement PCM must be programmed.

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming .

Is action complete?

--

Go to Step 8

--

8

  1. Review and records the scan tool Fail Records information.
  2. Clear the DTCs.
  3. Operate the vehicle within the Fail Records conditions.
  4. Monitor the scan tool Specific DTC Information for DTC P0462 until the test runs.

Does the scan tool indicate that DTC P0462 failed this ignition?

--

Go to Step 2

System OK