GM Service Manual Online
For 1990-2009 cars only

EVAP Canister Inspection

Tools Required

J 23738-A Hand Vacuum Pump


    Object Number: 845592  Size: SH
  1. Remove the EVAP canister. Refer to Evaporative Emission Canister Replacement .
  2. Visually inspect the EVAP canister, especially at the arrows, for any cracks or damage.

  3. Object Number: 845600  Size: SH

    Caution: Do not breathe the air through the EVAP component tubes or hoses. The fuel vapors inside the EVAP components may cause personal injury.

  4. Plug the vent port (4). The vent port will remain plugged for all the tests.
  5. Block the purge port (3) closed.
  6. Blow air with a pressure of 1.7 kPa (0.5 in Hg/0.25 psi) into the EVAP vapor port (2).
  7. Verify that air flows out of drain hose (1).

  8. Object Number: 845601  Size: SH
  9. Block the purge port (3) and the drain hose (1) closed.
  10. Blow air with a pressure of 1.7 kPa (0.5 in Hg/0.25 psi) into the EVAP vapor port (4).
  11. Verify that air does not flow out of the air inlet port (2).

  12. Object Number: 845603  Size: SH
  13. Block the air inlet port (2) closed.
  14. Connect the J 23738-A or an equivalent hand vacuum pump to the purge port (1).
  15. Apply a vacuum of 3.5 kPa (1.0 in Hg/0.5 psi) to purge port (1) with the hand vacuum pump.
  16. Verify that the vacuum holds while the air inlet port (2) is closed.
  17. Open the air inlet port (2) and verify that the vacuum is released.

  18. Object Number: 845604  Size: SH
  19. Block the air inlet port (1) closed.
  20. Connect the J 23738-A or an equivalent hand vacuum pump to the EVAP vapor port (3).
  21. Apply a vacuum of 3.5 kPa (1.0 in Hg/0.5 psi) to the EVAP port (3) with the hand vacuum pump.
  22. Verify that there is vacuum pressure at the purge port (2).
  23. Replace the EVAP canister if the canister failed any of the inspections or tests. Refer to Evaporative Emission Canister Replacement .

EVAP Canister Purge Valve Inspection


    Object Number: 832009  Size: SH

    Caution: Do not breathe the air through the EVAP component tubes or hoses. The fuel vapors inside the EVAP components may cause personal injury.

  1. Remove the EVAP canister purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .
  2. Use a DMM in order to measure the resistance of the EVAP canister purge valve.
  3. Measure
    The EVAP canister purge valve resistance should be 27-33 ohms at 20°C (68°F).

  4. Replace the EVAP canister purge valve if the resistance is not within the specified range. The solenoid will damage the powertrain control module (PCM) if the resistance value is less than 27 ohms.
  5. Check the PCM and replace if necessary. Refer to Powertrain Control Module Replacement .

  6. Object Number: 832011  Size: SH
  7. Check for continuity of each terminal to the valve body.
  8. Replace the EVAP canister purge valve if continuity is present.

  9. Object Number: 832012  Size: SH
  10. Blow air into one of the ports. The air should NOT flow through the opposite port.
  11. Apply battery voltage across the terminals of the EVAP canister purge valve.
  12. Blow air into the one port. The air should flow easily to the opposite port.
  13. Replace the EVAP canister purge valve if the valve failed either test. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .

EVAP Pressure Switching Solenoid Inspection


    Object Number: 621422  Size: SH

    Caution: Do not breathe the air through the EVAP component tubes or hoses. The fuel vapors inside the EVAP components may cause personal injury.

  1. Remove the EVAP pressure switching solenoid. Refer to Evaporative Emission Pressure Switching Solenoid Replacement .
  2. Use a DMM in order to measure the resistance of the EVAP pressure switching solenoid.
  3. Measure
    The EVAP pressure switching solenoid resistance is 37-44 ohms at 20°C (68°F).

  4. Replace the EVAP pressure switching solenoid if the resistance is not within the specified range. The solenoid will damage the PCM, if the resistance value is less than 27 ohms.

  5. Object Number: 623304  Size: SH
  6. Check for continuity on each terminal to the valve body.
  7. Replace the EVAP pressure switching solenoid if continuity is present. Refer to Evaporative Emission Pressure Switching Solenoid Replacement .

  8. Object Number: 621420  Size: SH
  9. Blow air into the inboard port. The air should NOT flow through the valve and out of the outboard port.
  10. Apply battery voltage across the terminals of the EVAP pressure switching solenoid.
  11. Blow air into the inboard port and air should flow through the valve and out of the outboard port.
  12. Replace the EVAP pressure switching solenoid if the solenoid failed either test. Refer to Evaporative Emission Pressure Switching Solenoid Replacement .

EVAP Canister Vent Valve Inspection


    Object Number: 832002  Size: SH

    Caution: Do not breathe the air through the EVAP component tubes or hoses. The fuel vapors inside the EVAP components may cause personal injury.

  1. Disconnect the EVAP vent solenoid electrical connector.
  2. Use a DMM in order the measure the solenoid resistance value.
  3. Measure
    The resistance should be between 25-30 ohms at 20°C (68°F).

  4. Replace the solenoid if the resistance is not within the specified range. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement .

  5. Object Number: 832003  Size: SH
  6. Use a DMM in order the check for continuity between each solenoid terminal and solenoid housing.
  7. Measure
    The DMM has to read infinite (OL).

  8. Replace the EVAP vent solenoid valve if the resistance is not within specification. A shorted valve will cause damage to the PCM.

  9. Object Number: 832006  Size: SH
  10. Blow air through the upper port of the EVAP vent valve. Air has to flow freely through the lower port.
  11. Replace the valve if the air does not flow through the upper port. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement .

  12. Object Number: 832007  Size: SH
  13. Apply battery voltage across the solenoid terminals.
  14. Blow air through the upper port of the solenoid. Air should NOT flow through the valve.
  15. Replace the solenoid if the solenoid fails any of the tests. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement .