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Home >> Chevrolet >> 2003 >> Tracker 2D Utility, 4WD, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - 2.0L >> Diagnostic Tests >> DTC P0456: EVAP System - Very Small Leak Detected >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
  2. Are any EVAP DTCs set other than a DTC P0455 or DTC P0456? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Observe the Fuel Tank Pressure (FTP) sensor parameter on scan tool. Remove fuel filler cap. Is fuel tank pressure within 0.0-0.5 in. H2O (0.0-0.9 mm Hg) with fuel filler cap removed? If yes, go to next step. If no, go to DTC P0451: FUEL TANK PRESSURE SENSOR PERFORMANCE .
  4. Visually inspect the entire EVAP control system for loose hose connections, damaged or deteriorated hoses, clogged hoses, missing or damaged components, or loose or incorrect fuel filler cap. Was a problem found? If yes, go to step  7. If no, go to next step.
    5. NOTE: Ensure vehicle underbody temperature is similar to the ambient temperature and allow surrounding air to stabilize before starting this diagnostic procedure. System flow will be less with higher temperatures.
  5. Turn ignition off. Connect Evaporative Emissions System Tester (J-41413-200) power supply clips to a known-good 12-volt source. Install Fuel Tank Cap Adapter (J-41415-30) to fuel fill pipe. Connect fuel fill cap to the J-41415-30. Connect the nitrogen/smoke supply hose to the J-41415-30. Turn ignition on, with engine off. Command the EVAP vent solenoid closed with scan tool. Turn the nitrogen/smoke valve on the control panel to SMOKE. Use the remote switch to introduce smoke into the EVAP system. Disconnect EVAP purge line from purge solenoid. Re-connect EVAP purge line to purge solenoid once smoke is observed. Continue to introduce smoke into EVAP system for an additional 60 seconds. Inspect the entire EVAP system for exiting smoke with the High Intensity White Light (J-41413-SPT). Continue to introduce smoke at 15 second intervals until leak source has been located. Did you locate and repair a leak source? If yes, go to next step. If no, go to step  7.
  6. Repair or replace any leaking or faulty EVAP control system components. After repairs, go to step  24.
  7. Check for any of the following conditions at the EVAP canister purge valve: No manifold vacuum from intake manifold vacuum port, leaking or damaged vacuum hoses, or restricted vacuum hoses or passages. Repair any condition found. Was a repair necessary? If yes, go to step  24. If no, go to next step.
  8. Turn ignition on, with engine off. Disconnect vacuum hoses to the EVAP canister purge valve from the intake manifold and from the EVAP canister. Blow air into the vacuum hose that was disconnected from the EVAP canister. Air should not pass through the EVAP canister purge valve and exit from intake manifold hose. Command the EVAP canister purge valve ON and adjust the duty cycle to 100 percent with scan tool. Blow air into the vacuum hose that was disconnected from the EVAP canister. Air should pass through the EVAP canister purge valve and exit from the intake manifold hose. Does the EVAP canister purge valve pass both inspections? If yes, go to next step. If yes, go to step  17.
  9. Turn ignition off. Remove EVAP canister vent valve. Blow air into the EVAP canister vent valve port, located on the side that was connected to the EVAP canister air filter. Did air pass through to the other side of the EVAP canister vent valve? If yes, go to next step. If no, go to step  20.
  10. Turn ignition on, with engine off. Command EVAP canister vent valve ON using scan tool. Blow air into the EVAP canister vent valve port, located on the side that was connected to the EVAP canister air filter. Was the air unable to pass through the EVAP canister vent valve? If yes, go to next step. If no, go to step  18.
  11. Continue to blow air into the EVAP canister vent valve. Command EVAP canister vent valve OFF with scan tool. Did the air pass through the EVAP canister vent valve when scan tool commanded the vent valve OFF? If yes, go to next step. If no, go to step  18.
  12. Disconnect vacuum/vapor hoses from EVAP canister. Blow air into the tank port of the EVAP canister. There should be no restriction of air flow through the canister and out the purge pipe and the air port. Did the EVAP canister pass the test? If yes, go to next step. If no, go to step  15.
  13. Remove Fuel Tank Pressure (FTP) control valve. Connect a vacuum hose to the canister side port of the FTP control valve. Important: There will be some resistance, but air should flow steadily. Blow air into the hose on the FTP control valve. Did the air flow through the valve to the tank port side? If yes, go to next step. If no, go to step  21.
    14. NOTE: The FTP control valve allows vapor to flow from the fuel tank to the canister when fuel tank pressure is greater than canister pressure by more than 0.5 psi (3.5 kPa).
  14. Move the vacuum hose to the fuel tank port of the FTP control valve. Blow hard into the hose connected to the tank port side of the FTP control valve. Air should flow easily through the valve and out of the canister port. Did the FTP control valve pass this test? If yes, go to step  16. If no, go to step  21.
  15. Replace EVAP canister. After repairs, go to step  25.
  16. Inspect EVAP canister air filter and hoses for restrictions or blockage. Repair as necessary. Was a repair necessary? If yes, go to step  24. If no, go to DIAGNOSTIC AIDS .
  17. Connect a test light from battery voltage to the purge valve control circuit by backprobing at the PCM. Command the EVAP canister purge valve ON and adjust the duty cycle to 100 percent with scan tool. Does the test light flash and then illuminate steadily at the 100 percent duty cycle? If yes, go to step  22. If no, go to step  19.
  18. Connect a test light from battery voltage to the vent valve control circuit by backprobing at the PCM. Command the EVAP canister vent valve ON using scan tool. Does the test light illuminate only when the valve is commanded ON? If yes, go to step  20. If no, go to next step.
  19. Test for an intermittent and for a poor connection at the PCM. Repair as necessary. Was a repair necessary? If yes, go to step  24. If no, go to step  23.
  20. Replace EVAP canister vent valve. After repairs, go to step  24.
  21. Replace FTP control valve. After repairs, go to step  24.
  22. Replace EVAP canister purge valve. After repairs, go to step  24.
  23. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  24. Turn ignition off. Remove DOME fuse (located in passenger compartment fuse block). Reinstall DOME fuse. Reset radio clock time. Start engine. Operate the vehicle within the Conditions for Running the DTC or until the DTC P0456 diagnostic test has run. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  25. With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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