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HOMESERVICE MANUALSCHEVROLET1997CHEVY EXPRESS G3500, VAN CARGO, 6.5 FREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 107 (ENGINE CONTROLS - SYSTEM & COMPONENT TESTING - 4.3L)EMISSION SYSTEMS & SUB-SYSTEMSFUEL EVAPORATION CONTROLEVAP CONTROL SYSTEM DIAGNOSIS (ENHANCED SYSTEM)
1997 Chevrolet Chevy Express G3500, Van Cargo, 6.5 F

EVAP Control System Diagnosis (Enhanced System)

1997 Chevrolet Chevy Express G3500, Van Cargo, 6.5 FSECTION EVAP Control System Diagnosis (Enhanced System)
WARNING: This page is about a different car, the 1998 GMC Savana, 1998 Chevrolet Chevy Van, and 1998 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
  1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in TESTS W/CODES - 4.3L article.
  2. Retrieve DTCs. If DTC P0446, P0452 or P0453 does not exist, go to next step. If DTC P0446, P0452 or P0453 exists, perform appropriate DTC test. See TESTS W/CODES - 4.3L article.
  3. Turn ignition switch to LOCK position. Remove gas cap. Turn ignition switch to RUN position. Observe fuel tank pressure on scan tool. If -1-1 in. H2O exists, go to next step. If -1-1 in. H2O does not exist, perform FUEL TANK PRESSURE SENSOR DIAGNOSIS.
  4. Install gas cap. Connect Enhanced Pressure Purge Diagnosis Tester (J-41413) to EVAP service port. Using scan tool, command EVAP vent valve on. Attempt to pressurize EVAP system to 5 in. H2O. If EVAP system pressurizes and holds pressure, go to next step. If EVAP system does not pressurize and hold pressure, go to step 6).
  5. Maintain 5 in. H2O in EVAP system by turning rotary switch on tester to HOLD position. Observe fuel tank pressure on scan tool. If 5 in. H2O does not exist, go to step 8). If 5 in. H2O exists, go to step 9).
  6. Disconnect fuel tank vapor line and EVAP purge line from EVAP canister. Plug EVAP canister fuel tank vapor port. Connect vacuum pump to EVAP canister purge port. Using scan tool, ensure EVAP vent valve is still commanded on. Attempt to apply 5 in. Hg to EVAP canister. If 5 in. Hg can not be obtained or held, go to next step. If 5 in. Hg can be obtained and held, go to step 12).
  7. Leave system connected as described in step 6). Disconnect vent line at EVAP canister vent valve. Plug disconnected line. Attempt to apply 5 in. Hg to EVAP canister. If 5 in. Hg cannot be obtained or held, go to step 11). If 5 in. Hg can be obtained and held, go to step 17).
  8. Disconnect fuel tank vapor line from EVAP canister. Using enhanced EVAP pressure purge diagnostic tester, attempt to pressurize EVAP system to 5 in. H2O. If 5 in. H2O cannot be obtained and held with pressure applied, go to step 15). If 5 in. H2O can be obtained and held, go to step 18).
  9. Disconnect purge line at EVAP canister. Connect vacuum gauge to disconnected line. Start engine and let idle. Using scan tool, command EVAP purge solenoid to 100 percent while observing vacuum gauge. If 12 in. H2O or greater does not exist, go to next step. If 12 in. H2O or greater exists, check the following and repair as necessary:
    • Poor connection at PCM.
    • Misrouted, damaged or disconnected vacuum line.
    • Missing or damaged EVAP system components.
    • Poor connections at EVAP system components.
  10. Disconnect purge line from EVAP purge solenoid valve. Connect vacuum gauge to disconnected line. Start engine and let idle. Using scan tool, command EVAP purge solenoid to 100 percent while observing vacuum gauge. If 12 in. H2O or greater does not exist, go to step 16). If 12 in. H2O or greater exists, go to step 14).
  11. Check vent hose for possible cause of a vacuum leak. If vacuum leak does not exist, go to step 18). If leak exists, repair as necessary and go to step 19).
  12. Check for the following: missing or defective gas cap, disconnected or leaking fuel tank vapor lines or disconnect or damaged EVAP purge line. If problem exists, repair as necessary and go to next step. If problem does not exist, go to step 19).
  13. Using scan tool, command EVAP vent valve on. Using enhanced EVAP pressure purge diagnostic tester, pressurize EVAP system to 15 in. H2O. Find leak in EVAP system and repair as necessary. After repair is complete, go to step 19).
  14. Repair restriction in EVAP purge line and go to step 19).
  15. Repair restriction in EVAP fuel tank vapor line and go to step 19).
  16. Replace EVAP canister purge solenoid valve and go to step 19).
  17. Replace EVAP canister vent valve and go to step 19).
  18. Replace EVAP canister and go to next step.
  19. Turn ignition switch to RUN position. Using scan tool, turn EVAP vent valve on. Using enhanced EVAP pressure purge diagnostic tester, pressurize EVAP system to 15 in. H2O. Turn rotary switch on tester to HOLD position. If pressure decreases to less than 10 in. H2O within 2 minutes, go to step 2). If pressure does not decrease to less than 10 in. H2O within 2 minutes, go to next step.
  20. Clear DTCs. Using scan tool, perform SERVICE BAY TEST for EVAP system. If scan tool does not display any DTCs, system is okay at this time. If scan tool displays any DTCs, perform appropriate DTC test. See TESTS W/CODES - 4.3L article.
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