Content .. 2425 2426 2427 2428 ..
Chevrolet Silverado / GMC Sierra. Manual - part 2427
Circuit/System Description
The primary fuel level sender and the secondary fuel level sender changes resistance based on fuel
level. The engine control module (ECM) monitors the signal circuits of the primary fuel level
sender and the secondary fuel level sender in order to determine the fuel level. When the fuel tank
is full, the resistances of both fuel level senders are low and the ECM senses a low signal voltage
on both the signal circuits of the primary fuel level sender and the secondary fuel level sender.
When the fuel tanks are empty, the resistances of the fuel level senders are high and the ECM
senses a high signal voltage. The ECM uses the signal circuits of the primary fuel level sender and
the secondary fuel level sender 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 secondary 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
Circuit
Short to
Ground
High
Resistance
Open
Short to
Voltage
Signal
Performance
Fuel Level Sensor Signal
Secondary
P2067
1
P2068
P2068
P2066
Fuel Level Sensor Low
Reference
-
1
P2068
P2068
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
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.
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 secondary 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 value, test the secondary signal circuit terminal C for a
short to ground. If the circuit tests normal, replace the ECM.
3. If all circuits test normal, test or replace the secondary fuel level sensor.
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Component Testing
1. Ignition OFF, remove the secondary 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 secondary 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 P2068
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 P2068
Fuel Level Sensor 2 High Voltage
Diagnostic Fault Information
Short to
High
Short to
Signal
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Displays and Gages - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Circuit/System Description
The primary fuel level sender and the secondary fuel level sender changes resistance based on fuel
level. The engine control module (ECM) monitors the signal circuits of the primary fuel level
sender and the secondary fuel level sender in order to determine the fuel level. When the fuel tank
is full, the resistances of both fuel level senders are low and the ECM senses a low signal voltage
on both the signal circuits of the primary fuel level sender and the secondary fuel level sender.
When the fuel tanks are empty, the resistances of the fuel level senders are high and the ECM
senses a high signal voltage. The ECM uses the signal circuits of the primary fuel level sender and
the secondary fuel level sender 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 9-16 volts.
Conditions for Setting the DTC
The secondary 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.
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.
Circuit
Ground Resistance
Open
Voltage Performance
Fuel Level Sensor Signal
Secondary
P2067
1
P2068
P2068
P2066
Fuel Level Sensor Low
Reference
-
1
P2068
P2068
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
Content .. 2425 2426 2427 2428 ..