Silverado 2008

Fuel Tank (EVAP) Vapor Pressure Sensor

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Location



Specific to:

Chevrolet Silverado 1500 2008

The Fuel Tank Pressure Sensor (EVAP Pressure Sensor) is located on the fuel pump module, at the fuel tank.

Click image to see an enlarged view

Fig. Fuel tank pressure sensor and related components

Operation



Specific to:

Chevrolet Silverado 1500 2008

The Fuel Tank Pressure Sensor (EVAP Pressure Sensor) is a piezoelectric (pressure-sensitive) electronic device that monitors the pressure differential between the Evaporative Emission Control (EVAP) system and atmospheric pressure. The EVAP Pressure Sensor operates within a 5 volt DC reference range, and provides a linear input signal to the Powertrain Control Module (PCM).

Testing



Connection And Wiring Diagnosis

Specific to:

Chevrolet Silverado 1500 2008

Refer to the Electrical Wiring Diagram for component and connector locations, connector views, and circuit-specific information.

Many intermittent open or short circuits may be caused by wiring harness and connector movement due to vibration, engine torque, bumps and rough pavement, etc.

  1. Test the wiring harness and connectors by performing the following tests:

    Move the related connectors and wiring while monitoring the appropriate scan tool data.
     
    Move the related connectors and wiring with the component commanded ON and OFF. Using a suitable the scan tool, observe the component operation.
     
    With the engine running, move the related connectors and wiring while monitoring component operation.
     
    If harness or connector movement affects the data displayed, the component and system operation, or the engine operation, inspect and repair the harness or connections as necessary.
     

  2.  
  3. Test the connector terminal pins and/or wiring by performing the following tests:

    Inspect for incorrect mating of the connector halves, or terminals not fully seated in the connector body.
     
    Inspect for improperly formed or damaged terminals and test for incorrect terminal tension.
     
    Inspect for poor terminal to wire connections including terminals crimped over insulation. This requires removing the terminal from the connector body.
     
    Inspect for corrosion or water intrusion. Pierced or damaged insulation can allow moisture to enter the wiring. The conductor can corrode inside the insulation with little visible evidence. Look for swollen and/or brittle sections of wire in the suspect circuits.
     
    Inspect for wires that are broken inside the insulation by gently pulling on suspect sections of wiring.
     

  4.  

EVAP Pressure Sensor

Specific to:

Chevrolet Silverado 1500 2008

When testing the EVAP system for proper operation, there should always be a pressure differential between the fuel tank pressure and atmospheric pressure. If any of the tests reveal a pressure differential of less than .02- Hg (.067 kPa/.5mm Hg), the Powertrain Control Module (PCM) will interpret this condition as a leak.

  1. Verify the condition of the EVAP system by performing the following visual inspections:

    Ensure that the fuel filler cap is installed and properly secured.
     
    Inspect the charcoal canister for physical damage such as cracks, broken or cracked fittings, damage from road debris, or rodent damage.
     
    Inspect all EVAP control devices (EVAP and purge control system monitors, controllers, and actuators) for physical damage such as cracks, broken or cracked fittings, damage from road debris, or rodent damage.
     
    Inspect all hoses and vacuum line connections for proper routing and placement.
     
    Inspect all electronic control devices for proper electrical connections.
     
    Inspect the condition of all fittings and seals for damage, drying, or wear.
     
    Inspect the condition of all hoses and vacuum lines for displacement, damage, or wear.
     

  2.  

If any physical defects are evident, verify the operation of any questionable components before replacement.

  1. Verify the operation of the EVAP system by performing any or all the following tests:

    Using a suitable scan tool, perform an actuator (active) test to verify the correct operation of EVAP control devices (EVAP and purge control system monitors, controllers, and actuators).
     
    Using a smoke machine, verify that the EVAP system does not exhibit any physical leaks.
     
    Using a suitable EVAP system pressure tester, verify that the EVAP system is properly sealed against positive and negative pressure.
     
    Using a suitable EVAP system pressure tester along with a suitable scan tool, monitor the EVAP pressure under positive and negative pressure conditions.
     

  2.  

Verify the operation of all EVAP system components before replacing the EVAP Pressure Sensor.

Click image to see an enlarged view

Fig. EVAP Pressure Sensor Range Chart

Related Diagnostic Trouble Codes (DTC)

Specific to:

Chevrolet Silverado 1500 2008



Click image to see an enlarged view

Fig. Related Diagnostic Trouble Codes

EVAP Pressure Sensor Strategy

Specific to:

Chevrolet Silverado 1500 2008

The EVAP Pressure Sensor is the central component in the EVAP monitoring system. EVAP is a non-continuous monitor under Mode 6 OBD-II diagnostics, and operates within a 5 volt DC reference range. The Powertrain Control Module (PCM) utilizes EVAP Pressure Sensor data to monitor the fuel tank pressure differential, and will log a Diagnostic Trouble Code (DTC) in the event of any leak larger than .02- Hg (.067 kPa/.5mm Hg).

Removal & Installation



Specific to:

Chevrolet Silverado 1500 2008

  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Properly relieve the fuel system pressure.
  6.  
  7. Raise and support the vehicle safely.
  8.  
  9. Remove the fuel tank.
  10.  
  11. Remove the sensor.

    Click image to see an enlarged view

    Fig. Fuel tank pressure sensor and related components

  12.  

To install:


NOTE
Be sure to use new fasteners, as required.

  1. Position the valve on its mounting.
  2.  
  3. Continue the installation in the reverse order of the removal procedure.
  4.  

 
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