GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The fuel level sensor changes resistance based on fuel level. The powertrain control module (PCM) monitors the signal circuit of the fuel level sensor in order to determine fuel level. When the fuel tank is full, the sensor resistance is low and the PCM senses a low signal voltage. When the fuel tank is empty, the sensor resistance is high and the PCM senses a high signal voltage. The PCM uses the signal circuit of the fuel level sensor in order to calculate the total remaining fuel (percent) in the tank. The PCM sends the fuel level percent via the serial data circuit to the instrument panel cluster (IPC) in order to control the fuel gage. The fuel level information is also used for misfire and evaporative emission (EVAP) diagnostics.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0463 Fuel Level Sensor Circuit High Voltage

Conditions for Running the DTC

    • The ignition is ON.
    • The system voltage is between 11-16 volts.

Conditions for Setting the DTC

    • The fuel level signal voltage is less than 3.5 percent (greater than 3 volts).
    • The above condition is present for at least 10 seconds.

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 displays 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

    • Use the Freeze Frame and/or Failure Records data in order to locate an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data may aid in determining the number of miles since the DTC set. The Fail Counter and Pass Counter can also aid in determining the number of ignition cycles that the diagnostic reported a pass and/or fail. Operate the vehicle within the same freeze frame conditions, RPM, load, vehicle speed, temperature, etc. This will isolate when the DTC failed.
    • Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

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

  1. Tests for the proper operation of the circuit in the low voltage range.

Step

Action

Values

Yes

No

Schematic Reference: Instrument Cluster Schematics

Connector End View Reference: Powertrain Control Module Connector End Views , Engine Controls Connector End Views in Engine Controls - 3.5L, and Inline Harness Connector End Views in Wiring Systems

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the Fuel Level Sensor parameter in the powertrain control module (PCM) evaporative emission (EVAP) data list.

Does the scan tool indicate that the Fuel Level Sensor parameter is greater than the specified value?

4.5 V

Go to Step 3

Go to Diagnostic Aids

3

  1. Turn OFF the ignition.
  2. Disconnect C305.
  3. Connect a 3-amp fused jumper wire between the signal circuit of the fuel level sensor and the low reference circuit of the fuel level sensor (male terminal side).
  4. Turn ON the ignition, with the engine OFF.
  5. With a scan tool, observe the Fuel Level Sensor parameter.

Does the scan tool indicate that the Fuel Level Sensor parameter is less than the specified value?

0.4 V

Go to Step 6

Go to Step 4

4

Test the signal circuit of the fuel level sensor for the following:

    • An open
    • A high resistance
    • A short to voltage

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 5

5

Test the low reference circuit of the fuel level sensor for the following:

    • An open
    • A high resistance
    • A short to voltage

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

6

Test the signal circuit of the fuel level sensor for the following between C305 and the fuel level sensor.

    • An open
    • A high resistance
    • A short to voltage

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 7

7

Test the low reference circuit of the fuel level sensor for the following between C305 and the fuel level sensor.

    • An open
    • A high resistance
    • A short to voltage

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 8

8

Inspect for poor connections at the harness connector of the fuel level sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

9

Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

10

Replace the fuel level sensor. Refer to Fuel Level Sensor Replacement in Engine Controls - 3.5L.

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 12

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12

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK