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Home >> Isuzu >> 1996 >> Hombre XS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Testing >> DTC P0442 - EVAP System Small Leak Detected >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
  2. Turn ignition on, with engine off. Using scan tool, command EVAP canister purge valve and EVAP vent solenoid on and off. If purge valve and vent solenoid clicks, go to next step. If purge valve and/or vent solenoid dose not click, repair wiring or replace purge valve and/or vent solenoid as necessary.
  3. Remove fuel cap. Using scan tool, observe FUEL TANK VACUUM PRESSURE. If pressure is zero in. H2O, go to step 6). If pressure is more than zero in. H2O, go to next step.
  4. Disconnect battery, check fuel tank pressure sensor. See SYSTEM/COMPONENT TESTS article. Replace fuel tank pressure sensor or repair related wiring as necessary. If battery has not been disconnected, go to next step.
  5. Reinstall fuel cap. Using scan tool, command EVAP vent solenoid on (closed). Zero EVAP pressure and vacuum gauges on EVAP Pressure/Purge Cart (J-41413). Connect EVAP pressure/purge cart to EVAP service port. Pressurize EVAP system to 5 in. H2O. Monitor pressure using gauge on EVAP pressure/purge cart. If pressure is 4-6 in. H2O, go to next step. If pressure is not 4-6 in. H2O, check fuel tank pressure sensor. See SYSTEM/COMPONENT TESTS article. Replace fuel tank pressure sensor or repair related wiring as necessary.
  6. Turn ignition on, with engine off. Using scan tool, command EVAP vent solenoid on (closed). Using EVAP pressure/purge cart, pressurize EVAP system to 15 in. H2O. Set rotary switch on pressure/purge cart to HOLD, and observe EVAP pressure gauge. If pressure decreases to 10 in. H2O within 2 minutes, go to next step. If pressure does not decrease to 10 in. H2O within 2 minutes, see DIAGNOSTIC AIDS.
  7. Disconnect fuel tank vapor and EVAP purge hoses from EVAP canister. Plug canister fitting for fuel tank vapor hose. Connect a vacuum pump to EVAP purge hose fitting on EVAP canister. Ensure EVAP vent solenoid is still commanded on. Apply 5 in. Hg. If vacuum holds, go to step 11). If vacuum does not hold, go to next step.
  8. Check for disconnected or damaged vent hose. Also, check for damaged EVAP canister. Repair as necessary. After repair is completed, go to step 13). If no problem is found, go to next step.
  9. Replace defective EVAP vent solenoid. After repair is completed, go to step 13).
  10. Check for missing or faulty fuel cap. Check for disconnected or leaking fuel tank vapor hose or disconnected or damaged EVAP purge hose. Repair as necessary. After repair is completed, go to step 13). If no problem is found, go to next step.
  11. Using scan tool, command EVAP vent solenoid on. With EVAP pressure/purge cart connected to EVAP service port, attempt to pressurize EVAP system by leaving cart control knob in PRESSURIZE position. Using Ultrasonic Leak Detector (J-41416), locate and repair EVAP system leak. It may be necessary to partially lower fuel tank to examine hose connections at top of tank. After repair is completed, go to next step.
  12. Turn ignition on, with engine off. Using scan tool, command EVAP vent solenoid on (closed). Using EVAP pressure/purge cart, pressurize EVAP system to 15 in. H2O. Set rotary switch on pressure/purge cart to HOLD, and observe EVAP pressure gauge. If pressure decreases to 10 in. H2O within 2 minutes, system is functioning properly. If pressure does not decrease to 10 in. H2O within 2 minutes, repeat step 2).
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