Chevrolet Silverado / GMC Sierra. Service manual — part 2423

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 GMLAN
serial data circuit to the instrument cluster in order to control the fuel gage. The fuel information
is also used for misfire, evaporative emission (EVAP), and other onboard diagnostics.

Conditions for Running the DTC

The ignition is ON, with the engine running.

The system voltage is between 11-18 volts.

Conditions for Setting the DTC

The sender output is less than 0.5 volt.

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.

Circuit

Short to

Ground

High

Resistance

Open

Short to

Voltage

Signal

Performance

Fuel Level Sensor Signal

P0462

1

P0463,

P0464

P0463

P0461

Fuel Level Sensor Low
Reference

-

1

P0463,

P0464

P0463

P0461

1. Fuel Gage Inaccurate or Inoperative

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

Diagnostic Aids

A defective fuel level sensor most likely will not set DTC P0462. The sensor has a 500 ohm
default resistor that will prevent it from meeting the code setting criteria of this DTC. Look for
problems in the wiring and in the inline and harness connectors at the sensor and ECM.

Reference Information

Schematic Reference

Instrument Cluster Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Instrument Cluster Description and Operation

Electrical Information Reference

Circuit Testing

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Scan Tool Reference

Control Module References for Scan Tool Information

Circuit/System Verification

Ignition ON, verify the scan tool Fuel Tank Level Remaining parameter is between 4-98 percent.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the fuel level sensor.

2. Ignition ON, verify that the scan tool Fuel Tank Level Remaining parameter display is less

than 4 percent.

If greater than the specified range, test the signal circuit terminal C for a short to

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

ground. If the circuit tests normal, replace the ECM.

3. If all circuits test normal, test or replace the fuel level sensor.

Component Testing

1. Ignition OFF, remove the fuel level sender.

2. While sweeping the fuel level sensor through its full range of motion, test for a minimum

resistance value of less than 41 ohms and a maximum value greater than 119 ohms between
the signal terminal C and the low reference terminal B.

If not within the specified range, replace the fuel level sensor.

Component Testing

1. Ignition OFF, disconnect the harness connectors 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 between the signal
terminal C and the low reference terminal B.

If not within the specified range, replace the fuel level sensor.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Fuel Level Sensor Replacement (Extended Cab w/26 Gal Tank) or Fuel Level Sensor
Replacement (Regular Cab w/34 Gal Tank) or Fuel Level Sensor Replacement
(Regular Cab w/26 Gal Tank) for the 4.3L engine

Fuel Level Sensor Replacement (15 Reg Cab w/26 gal Tank) or Fuel Level Sensor
Replacement (15 Ext/Crew Cab w/26 gal Tank) or Fuel Level Sensor Replacement
(25 Ext/Crew Cab w/26 gal Tank) or Fuel Level Sensor Replacement (15/25
Reg/Ext/Crew Cab w/34 gal Tank) or Fuel Level Sensor Replacement (35
Reg/Ext/Crew Cab w/34 gal Tank) for the 4.8L, 5.3L, 6.0L, and 6.2L engines

Fuel Level Sensor Replacement (Cab/Chassis - Rear Tank) for the 6.6L engine

Control Module References for ECM replacement, setup, and programming

DTC P0463

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.

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0463

Fuel Level Sensor 1 High Voltage

Diagnostic Fault Information

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 GMLAN
serial data circuit to the instrument cluster in order to control the fuel gage. The fuel information
is also used for misfire, evaporative emission (EVAP), and other on-board diagnostics.

Conditions for Running the DTC

The ignition is ON, with the engine running.

The system voltage is between 11-18 volts.

Conditions for Setting the DTC

The sensor output is greater than 3.5 volts.

The above condition is present for greater than 30 seconds.

Action Taken When the DTC Sets

The fuel gage defaults to empty.

Circuit

Short to

Ground

High

Resistance

Open

Short to

Voltage

Signal

Performance

Fuel Level Sensor Signal

P0462

1

P0463,

P0464

P0463

P0461

Fuel Level Sensor Low
Reference

-

1

P0463,

P0464

P0463

P0461

1. Fuel Gage Inaccurate or Inoperative

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado