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EVAP Control System Diagnosis (3.4L)

  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing powertrain diagnostic system check, go to next step.
  2. Ensure vacuum and purge lines are connected. Check for loose or missing fuel filler cap. Install scan tool. Turn ignition on with engine off. Retrieve DTCs. If no DTCs are set, go to next step. If any DTCs are set, perform appropriate DTC test. See appropriate SELF-DIAGNOSTICS article.
  3. Turn ignition off. Remove fuel filler cap to relieve fuel pressure. Turn ignition on with engine off. Using scan tool, observe fuel tank pressure. If fuel tank pressure is zero in. H2 O, go to next step. If fuel tank pressure is not zero in. H2 O, perform DTC P0453 test. See appropriate SELF-DIAGNOSTICS article.
  4. Turn ignition off. Reinstall fuel cap. Install EVAP Pressure/Purge Diagnostic Station (J-41413) to EVAP service port and zero gauges. Turn ignition on with engine off. Using scan tool, capture and save freeze frame record for DTC 0440. Clear DTCs. Using scan tool, select EVAP PURGE/SEAL and seal EVAP system. Attempt to pressurize EVAP system to 5 in. H2 O by slowly turning diagnostic station rotary switch to PRESSURE position. Monitor pressure with switch in OFF/HOLD position. If fuel tank pressure is 5 in. H2 O, go to next step. If fuel tank pressure is not 5 in. H2 O, perform DTC P0440 test. See appropriate SELF-DIAGNOSTICS article.
  5. Maintain fuel tank pressure at 5 in. H2 O. Monitor pressure with switch in OFF/HOLD position. Using scan tool, observe fuel tank pressure. If fuel tank pressure is 5 in. H2 O, go to next step. If fuel tank pressure is not 5 in. H2 O, go to step  10.
  6. Command EVAP canister vent solenoid valve off to relieve pressure through vent solenoid valve. If EVAP pressure gauge decreases to about -5 in. H2 O within 2 minutes with rotary switch in OFF/HOLD position, go to next step. If EVAP pressure gauge does not decrease to about -5 in. H2 O within 2 minutes with rotary switch in OFF/HOLD position, perform DTC P0446 test. See appropriate SELF-DIAGNOSTICS article.
  7. Connect the in. Hg vacuum gauge of diagnostic station to EVAP purge solenoid valve (canister side). Turn ignition on with engine off. Using scan tool, select EVAP PURGE/SEAL and seal EVAP system. Start engine and let idle. Run engine from 1200-1500 RPM and observe vacuum level. If vacuum is near zero in. Hg, go to next step. If vacuum is not near zero in. Hg, go to step  11.
  8. Using scan tool, increase purge to 100 percent. Run engine from 1200-1500 RPM and observe vacuum level. If vacuum level is greater than 15 in. Hg, go to next step. If vacuum level is 15 in. Hg or less, go to step  12.
  9. Check for kinked or restricted canister purge line between EVAP purge solenoid valve and EVAP canister. Repair as necessary. After repairs, go to step  13.
  10. Check for restricted fuel tank vapor line or EVAP purge line. If problem exists, repair as necessary and go to step  13. If problem does not exist, perform DTC P0452 test. See appropriate SELF-DIAGNOSTICS article.
  11. Check EVAP purge solenoid valve and purge line for carbon contamination. Replace EVAP purge solenoid valve. After repairs, go to step  13.
  12. Check for no source vacuum to EVAP purge solenoid valve. If problem exists, repair as necessary and go to step  2. If problem does not exist, go to next step.
  13. Reconnect all previously disconnect EVAP system components and hardware. Turn ignition on with engine off. Using scan tool, select EVAP PURGE/SEAL and seal EVAP system. Pressurize EVAP system to 15 in. H2 O by slowly turning diagnostic station rotary switch to PRESSURE position. Monitor pressure with switch in OFF/HOLD position. If EVAP pressure gauge decreases to less than 10 in. H2 O within 2 minutes with rotary switch in OFF/HOLD position, perform DTC P0442 test. See appropriate SELF-DIAGNOSTICS article. If EVAP pressure gauge does not decrease to less than 10 in. H2 O within 2 minutes with rotary switch in OFF/HOLD position, system is okay.
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