For 1990-2009 cars

### 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 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 | P0463 | P0461
Fuel Level Sensor Low Reference Circuit | -- | P0463 P0464 | P0463 | P0461

### Circuit/System Description

The fuel level sensor changes resistance in response to the fuel level. The engine control module (ECM) monitors the signal circuit of the fuel level sensor in order to determine the fuel level. When the fuel tank is full, the sensor resistance is low and the ECM senses a low signal voltage. When the fuel tank is empty, the sensor resistance is high and the ECM senses a high signal voltage. The ECM uses the signal circuit of the fuel level sensor in order to calculate the percentage of remaining fuel in the tank. The ECM sends the fuel level percentage via the serial data circuit to the body control module (BCM). The BCM sends serial data messages to the instrument panel cluster (IPC) in order to control the fuel gage and display the fuel level percent.

### Conditions for Running the DTC

• | The ignition is ON, with the engine running.

• | The system voltage is between 9-16 volts.

### Conditions for Setting the DTC

• | The sensor output is greater than 2.9 volts.

• | The above condition is present for greater than 30 seconds.

### Action Taken When the DTC Sets

• | The fuel gage defaults to empty.

• | The low fuel indicator illuminates.

• | The ECM records the operating conditions at the time that the diagnostic test fails. The ECM 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 ECM receives a clear code command from the scan tool.

### 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 Verification

With the scan tool installed and the ignition ON, the Fuel Tank Level Remaining parameter in the ECM EVAP Data List indicates a value at or greater than 4 percent.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the fuel level sensor.
2. Ignition OFF, test for less than 1 ohm of resistance between the fuel level sensor low reference circuit terminal C and ground.

⇒ | If greater than the specified value, test the low reference circuit for a short to voltage or an open/high resistance. If the circuits tests normal, replace the ECM.

3. Install a 3-amp fused jumper wire between the fuel level sensor signal circuit terminal B and the fuel level sensor low reference circuit terminal C. Verify the Fuel Tank Level Remaining parameter and verify the Fuel Tank Level Remaining parameter is greater than 98 percent.

⇒ | If less than specified value, test the fuel level sensor signal and low reference circuits for a short to voltage or an open/high resistance. If the circuits test normal, replace the ECM.

4. If all circuits test normal, perform the fuel level sensor component test before replacing either the primary or secondary fuel level sensor.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the fuel level sensor.
2. While sweeping the fuel level sensor through its full range of motion, test for a minimum value less than 41 ohms and a maximum value greater than 119 ohms of resistance between signal terminal B and the low reference terminal C.

⇒ | If not within 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 the ECM replacement, setup and programming