Chevrolet Silverado / GMC Sierra. Manual — part 2432
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 high speed
GMLAN serial data to the body control module (BCM). The BCM then sends the fuel
information to the instrument panel cluster (IPC) via low speed GMLAN in order to display the
fuel gage. The fuel information is also used for misfire and evaporative emission (EVAP)
diagnostics.
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
Circuit
Ground Resistance
Open
Voltage 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
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Ignition ON, verify DTC P0461, P0462, P0463, or P0464 is not set
If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the fuel level sensor.
2. Ignition OFF, test for less than 1.0 ohm between the fuel level sensor low reference circuit
terminal B and ground.
If greater than the specified range, test the low reference circuit for an open/high
resistance. If the circuit tests normal, replace the ECM.
3. Install a Signal Generator and Instrument Panel Tester between the signal circuit terminal C
and ground.
4. Ignition ON, vary the signal generator resistance between 40-250 ohms. Verify that the scan
tool Fuel Tank Level Remaining parameter displays a range that varies between 5 and 95
percent as the signal generator resistance changes.
If not within the specified range, test the signal circuit for an open/high resistance. If
the circuits test normal, replace the ECM.
5. Vary the signal generator resistance between 40-250 ohms. Verify that the fuel gage
displays a range that varies between empty and full as the signal generator resistance
changes.
If the gage is incorrect, replace the IPC.
6. If all circuits test normal, perform the fuel level sensor component test before replacing 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
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
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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 the ECM or IPC replacement, setup, and programming
FUEL GAGE INACCURATE OR INOPERATIVE (DUAL TANK)
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.
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 circuits of the primary and secondary fuel level sensors in order to
determine the fuel level. When the fuel tanks are full, the sensor resistances are low and the ECM
senses a low signal voltage. When the fuel tanks are empty, the sensor resistances are high and the
Circuit
Short to
Ground
High
Resistance
Open
Short to
Voltage
Signal
Performance
Fuel Level Sensor Signal
P0462,
P2067
1
P0463,
P0464,
P2068
P0463,
P2068
P0461,
P2066
Fuel Level Sensor Low
Reference
-
1
P0463,
P0464,
P2068
P0463,
P2068
P0461,
P2066
1. Fuel Gage Inaccurate or Inoperative
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
ECM senses a high signal voltage. The ECM uses the signal circuits of the primary and secondary
fuel level sensors in order to calculate the percentage of remaining fuel in the tanks. The ECM
sends the fuel level percentage via high speed GMLAN serial data to the body control module
(BCM). The BCM then sends the fuel level information to the instrument panel cluster (IPC) via
low speed GMLAN in order to display the fuel level. The fuel information is also used for misfire
and evaporative emission (EVAP) diagnostics.
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 DTC P0461, P0462, P0463, P0464, P2066, P2067, or P2068 is not set
If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the primary and secondary fuel level
sensors.
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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