GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0463 : Fuel Level Sensor 1 Circuit High Voltage

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Fuel Level Sensor Reference Voltage Circuit

P0462

--

--

P0461

Fuel Level Sensor Signal Circuit

P0462

P0463, P0464, 1

P0463

P0461

Fuel Level Sensor Low Reference Circuit

--

P0463, P0464, 1

P0463

P0461

1. Fuel Gage Inaccurate or Inoperative

Circuit/System Description

The fuel level sender changes resistance based on the fuel level. The powertrain control module (PCM) monitors the signal circuit of the fuel level sender in order to determine fuel level. When the fuel tank is full, the sender resistance is low and the PCM senses a low signal voltage. When the fuel tank is empty, the sender resistance is high and the PCM senses a high signal voltage. The PCM uses the signal circuit of the fuel level sender in order to calculate the total remaining fuel percent in the tank. The PCM sends the fuel level message via the CAN serial data circuit to the body control module (BCM). The BCM sends the fuel level percent to the instrument panel cluster (IPC) via the class 2 data circuit to display on the fuel gage. The fuel level information is also used for misfire and evaporative emission (EVAP) diagnostics.

This diagnostic tests for a lower than normal fuel level sender signal.

Conditions for Running the DTC

The ignition is ON, with the engine ON.

Conditions for Setting the DTC

    • The fuel level signal is less than 3.5 percent.
    • The above condition is present for greater than 20 seconds.

Action Taken When the DTC Sets

    • The fuel gage defaults to empty.
    • 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

Using the Failure Records data may help locate an intermittent condition. If you cannot duplicate the DTC, the information in the Failure Records can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can help determine how many ignition cycles that the diagnostic test reported a pass and/or a fail.

Reference Information

Schematic Reference

    •  Instrument Cluster Schematics
    •  Engine Controls Schematics

Connector End View Reference

    •  Displays and Gages Connector End Views
    •  Engine Control Module Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Scan Tool Data List

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the fuel level sensors.
  2. Ignition OFF, test for less than 1 ohm of resistance between the low reference circuit and ground.
  3. If greater than 1 ohm, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the PCM.
  4. Ignition ON, install a 3-amp fused jumper between the signal circuit and the low reference circuit. Verify the scan tool Fuel Tank Level Remaining parameter is greater than 98 percent.
  5. If less than 98 percent, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the PCM.
  6. If all circuits test normal, test or replace the fuel level sensors.

Component Testing

Measure the resistance of the float arm of the fuel level sender while moving the float arm between 40-250 ohms.

If the resistance does not move smoothly across the specified range, replace the fuel level sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Fuel Level Sensor Replacement
    •  Control Module References for PCM replacement, setup, and programming