GM Service Manual Online
For 1990-2009 cars only

Inspection Procedure

Tools Required

J 41413 EVAP Pressure/Purge Diagnostic Station

Whenever the DTC diagnostics lead to a no trouble found or a purge solenoid replacement, proceed with the following charcoal canister diagnostics.

Notice: Use the EVAP Pressure/Purge Diagnostic Station J 41413 in order to provide a clean, dry, low pressure gas source. Do not substitute any other pressurized gas source. Damage may result to the EVAP system.


    Object Number: 20803  Size: SH
  1. Turn OFF the ignition.
  2. Remove the EVAP canister purge solenoid from the vehicle.
  3. Lightly tap the EVAP canister purge solenoid on a clean work area.
  4. Look for carbon particles existing from either of the vacuum ports.
  5. If no carbon release is evident, reinstall the components. Continue with the published service manual DTC procedures.
  6. If carbon is being released from either component, continue with this service procedure.
  7. Remove the charcoal canister from the vehicle.
  8. Turn off the main cylinder valve (1) on the EVAP purge/pressure diagnostic station J 41413 .
  9. Disconnect the black hose (4) that connects the nitrogen cylinder to the EVAP pressure/purge diagnostic station J 41413 at the pressure regulator (5).
  10. Using a section of the vacuum hose, connect one end onto the open fitting of the EVAP pressure/purge diagnostic station J 41413 pressure regulator (5).
  11. Connect the other end of the vacuum line side of the EVAP purge line at the vehicle.
  12. Turn on the main nitrogen cylinder valve (1).
  13. Continue to blow any debris from the purge line for 15 seconds.
  14. Return the J 41413 EVAP pressure/purge diagnostic station to its original condition by re-installing the black hose (4) disconnected in step 9.
  15. Replace the EVAP purge solenoid and the charcoal canister with the new components.
  16. Connect the EVAP pressure/purge diagnostic station J 41413 to the vehicle EVAP service port. Turn the four position switch to Purge.
  17. Start the engine. Allow the engine to reach the operating temperature.
  18. Open the throttle until the engine speed reaches 2000 RPM.
  19. Note the H2O vacuum gauge on the EVAP cart. The vacuum should read greater than 15 inches H2O.
  20. If the vacuum is less than 15 inches H2O, perform a complete throttle body service including a cleaning of the purge ports as outlined in the service manual. Go to step 1.
  21. If the vacuum is more than 15 inches H2O, continue with the published service manual diagnostics.