EVAP Control System Diagnosis (Except 2.2L & 3.4L)

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.
Retrieve DTCs. If DTC P0440, P0442, P0446, P0452, P0453, P0461, P0462, P0463 or P1441 is not set, go to next step. If DTC P0440, P0442, P0446, P0452, P0453, P0461, P0462, P0463 or P1441 is set, perform appropriate DTC test. See appropriate SELF-DIAGNOSTICS article.
Inspect EVAP system for the following:
- Loose, incorrect, defective or missing fuel filler cap.
- Improperly routed, kinked, or damaged EVAP system purge lines.
- Damaged EVAP system components.
- Loose, missing or damaged service port dust cap and/or Schrader valve.
If problem exists, repair as necessary and go to step 25. If problem does not exist, go to next step.
Before proceeding with service bay test, ensure DTCs are cleared, battery voltage is 10.5-17.5 volts, fuel level is 15-85 percent, and with ignition on engine temperature is less than 176°F (80°C). Scan tool will display TEST ABORTED when service bay test is activated if the listed criteria are not met. Using scan tool, capture and save freeze frame records. Clear DTCs. Using scan tool, perform service bay test for EVAP system. If vehicle does not pass service bay test, go to next step. If vehicle passes service bay test, inspect EVAP system for the following:
- Loose, incorrect, defective or missing fuel filler cap.
- Missing or damaged EVAP canister fuel vapor and purge line fitting "O" rings.
- Cracked or punctured EVAP canister.
- Improperly routed, kinked, or damaged EVAP system purge and vapor lines.
- Disconnected or damaged EVAP purge line, vent hose or fuel tank vapor line.
- Poor connection at VCM, backed-out terminals, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connection
- Damaged EVAP purge solenoid valve, EVAP canister vent solenoid valve of fuel tank pressure sensor wiring harnesses.
- Kinked, pinched, plugged or restricted EVAP purge or fuel tank vapor line.
Turn ignition off. Connect a vacuum gauge directly to purge connection of EVAP purge solenoid valve. Start engine and let idle. Using scan tool, command EVAP purge solenoid valve to 100 percent purge. If vacuum is 12 in. Hg or more, go to next step. If vacuum is less than 12 in. Hg, go to step 11.
Turn ignition off. Disconnect fuel tank vapor line and EVAP purge line from EVAP canister. Plug EVAP canister fuel tank vapor port. Connect a hand-held vacuum pump to EVAP canister purge port. With ignition on, using scan tool, command EVAP vent solenoid valve on. Attempt to apply 5 in. Hg to EVAP canister. If 5 in. Hg can be obtained and held, go to step 9. If 5 in. Hg cannot be obtained or held, go to next step.
Leave system connected as described in step 6. Disconnect vent line at EVAP canister vent solenoid valve. Plug disconnected vent line. Attempt to apply 5 in. Hg to EVAP canister. If 5 in. Hg can be obtained and held, go to step 15. If 5 in. Hg cannot be obtained or held, go to next step.
Inspect for leaks in EVAP vent line from EVAP canister to EVAP vent solenoid valve. Replace as necessary. If problem exists, go to step 25. If problem does not exist, go to step 21.
Turn ignition off. Remove plug and hand-held vacuum pump. Reconnect EVAP canister purge and fuel tank vapor lines. Connect EVAP Pressure/Purge Diagnostic Station (J-41413) to EVAP system service port. Using scan tool, command EVAP vent solenoid valve on. Attempt to pressurize EVAP system to 15 in. H₂ O. DO NOT pressurize EVAP system to more than 15 in. H₂ O. Using Ultrasonic Leak Detector (J-41416), locate and repair EVAP system leak. If problem exists, go to step 25. If problem does not exist, go to next step.
Check EVAP system for restrictions. Repair as necessary. If problem exists, go to step 25. If problem does not exist, go to step 22.
Turn ignition on with engine off. Disconnect EVAP purge solenoid valve connector. Connect a test light between ground and ignition feed circuit of EVAP purge solenoid valve connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 13.
Connect a test light between ignition feed circuit and control circuit of EVAP purge solenoid valve connector. Using scan tool, command EVAP purge solenoid valve on. If test light illuminates, go to step 19. If test light does not illuminate, go to step 14.
Check for and repair cause of no power to EVAP purge solenoid valve ignition feed circuit. Possible causes may be:
- Open ignition feed circuit.
- Shorted ignition feed circuit (open fuse).
- Shorted EVAP purge solenoid valve (open fuse).
- No power to EVAP purge solenoid valve fuse (open Maxi-fuse, fuse link, etc.).
After repairs, go to step 25.
Check for open in EVAP purge solenoid valve control circuit. Repair as necessary. If problem exists, go to step 25. If problem does not exist, go to step 24.
Turn ignition on with engine off. Disconnect EVAP canister vent solenoid valve connector. Connect a test light between ground and ignition feed circuit of EVAP canister vent solenoid valve connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 17.
Connect a test light between ignition feed circuit and control circuit of EVAP canister vent solenoid valve connector. Using scan tool, command EVAP canister vent solenoid valve on. If test light illuminates, go to step 20. If test light does not illuminate, go to step 18.
Check for and repair cause of no power to EVAP canister vent solenoid valve ignition feed circuit. Possible causes may be:
- Open ignition feed circuit.
- Shorted ignition feed circuit (open fuse).
- Shorted EVAP canister vent solenoid valve (open fuse).
- No power to EVAP canister vent solenoid valve fuse (open Maxi-fuse, fuse link, etc.).
After repairs, go to step 25.
Check for open in EVAP canister vent solenoid valve control circuit. Repair as necessary. If problem exists, go to step 25. If problem does not exist, go to step 24.
Check EVAP purge solenoid valve and purge line for carbon contamination. Replace EVAP purge solenoid valve. After repairs, go to step 25.
Replace EVAP canister vent solenoid valve. After repairs, go to step 25.
Replace EVAP vapor canister. After repairs, go to step 25.
Relieve all system pressure. Using scan tool, select PURGE/SEAL. Turn EVAP purge solenoid valve on to varying vacuum levels with engine running and quickly SEAL system using scan tool. Leaving EVAP purge solenoid valve on for higher percents or longer times will develop a higher level of vacuum. Maximum of 8.5 in. H₂ O of vacuum can be applied to EVAP system using scan tool. While system is sealed, compare EVAP pressure/purge diagnostic station vacuum gauge (H₂ O) to vacuum indicated on scan tool from EVAP fuel tank pressure sensor. Allow system to stabilize for a few seconds. If values indicate the same amount of vacuum in EVAP system within 2 in. H₂ O, go to step 3. If values do not indicate the same amount of vacuum in EVAP system within 2 in. H₂ O, go to next step.
Replace fuel tank pressure sensor. After repairs, go to step 25.
Replace VCM and reprogram. Perform VTD password relearn procedure and crankshaft variation learn procedure. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION. After repairs, go to next step.
Using scan tool, clear DTCs. Start engine and let idle until normal operating temperature is obtained. Using scan tool, select DTC, and then SPECIFIC DTC. Enter the DTC number which was set. Operate vehicle under conditions for setting DTC until scan tool indicates the diagnostic ran. If scan tool indicates the diagnostic passed, go to next step. If scan tool does not indicate the diagnostic passed, go to step 2.
If scan tool displays any additional undiagnosed DTCs, perform appropriate DTC test. See appropriate SELF-DIAGNOSTICS article. If scan tool does not display any additional undiagnosed DTCs, system is okay.