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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 51 (Engine Control System - Self-Diagnostics - 4.2L) >> Diagnostic Tests >> DTC P0442: EVAP System - Small Leak >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Are DTCs P0440, P0446, P0452, P0453, or P1441 also set? If yes, see DTC P0440: EVAP SYSTEM - LARGE LEAK  , DTC P0446: EVAP VENT VALVE PERFORMANCE  , DTC P0452: FUEL TANK PRESSURE SENSOR - LOW VOLTAGE  , DTC P0453: FUEL TANK PRESSURE SENSOR - HIGH VOLTAGE  or DTC P1441: EVAP SYSTEM FLOW DURING NON-PURGE  . If no, go to next step.
  3. Inspect the EVAP system for the following conditions:
    • A loose, incorrect, faulty, or missing fuel tank fill cap.
    • Damaged or disconnected EVAP system purge lines.
    • A damaged EVAP system component.
    • A loose, missing, or damaged service port Schrader valve.

    Did you find and correct the condition? If yes, go to step  6 . If no, go to next step.

    4. NOTE: The following steps require the J 41413 EVAP Pressure/Purge Diagnostic Station and the J 41415-40 Fuel Tank Cap Adapter. Always zero the EVAP pressure and vacuum (in. H2O) gages on the EVAP pressure/purge diagnostic station before proceeding with diagnosis.
  4. Install the fuel tank cap adapter. Connect the EVAP pressure/purge diagnostic station and the fuel tank cap to the fuel tank cap adapter. Turn ON the ignition, with the engine OFF. Use a scan tool to clear the DTCs from the PCM. Command the EVAP vent valve ON with a scan tool. Pressurize the EVAP system to 5 in. H2O with the EVAP pressure/purge diagnostic station. Place the control knob on the EVAP pressure/purge diagnostic station to the OFF/HOLD position. Monitor the EVAP system pressure on the EVAP pressure/purge diagnostic station for 5 minutes. Does the EVAP system pressure remain constant? If yes, see DIAGNOSTIC AIDS  . If no, go to next step.
    5. NOTE: It may be necessary to partially lower the fuel tank to inspect components located in the upper portion of the tank.
  5. With the pressure/purge diagnostic station, continuously attempt to pressurize the EVAP system. With the J 41416 ultrasonic leak detector inspect for leaks in the following locations:
    • The EVAP system purge pipe.
    • The EVAP vapor pipe.
    • The EVAP vent hose/pipe.
    • The fuel fill pipe/hose and fuel fill cap.
    • The EVAP canister.
    • The EVAP canister vent valve.
    • The EVAP canister purge valve.
    • The fuel sender assembly and/or seal.
    • The FTP sensor seal.
    • The fill limiter vent valve, pressure relief valve, rollover valves, and fuel tank.

    Did you find and repair the condition? If yes, go to next step. If no, see DIAGNOSTIC AIDS  .

  6. Turn ON the ignition, with the engine OFF. With a scan tool, clear the DTCs. Command the EVAP vent valve ON with a scan tool. Pressurize the EVAP system to 5 in. H2O with the EVAP pressure/purge diagnostic station. Place the control knob on the EVAP pressure/purge diagnostic station to the OFF/HOLD position. Monitor the EVAP system pressure on the EVAP pressure/purge diagnostic station for 5 minutes. Does the EVAP system pressure remain constant? If yes, go to next step. If no, go to step  2 .
  7. Observe the stored information, Capture Info with a scan tool. 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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