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Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Isuzu Trooper. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform ON-BOARD DIAGNOSTIC II SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD-II system check, go to next step.
  2. Using scan tool, check if DTC P0452 or P0453 are stored. If DTCs are present, diagnose these DTCs before proceeding. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no other DTCs are set, go to next step.
  3. Turn ignition off. Remove fuel cap. Turn ignition on. Using scan tool, observe FUEL TANK PRESSURE parameter. FUEL TANK PRESSURE parameter should display 1.51 volts. If parameter is as specified, reinstall fuel cap and go to next step. If parameter is not as specified, go to DTC P0452: FUEL TANK PRESSURE SENSOR LOW VOLTAGE  or DTC P0453: FUEL TANK PRESSURE SENSOR HIGH VOLTAGE  .
  4. Start engine. Using scan tool, observe FUEL TANK PRESSURE parameter. FUEL TANK PRESSURE parameter should display 1.47-1.51 volts. If parameter is as specified, go to step  7. If parameter is not as specified, go to step  6.
  5. Turn ignition off. Disconnect fuel tank vapor and EVAP purge lines from EVAP canister. EVAP canister is attached to frame rail under rear of vehicle. Plug fuel tank vapor line fitting at EVAP canister. Connect a hand vacuum pump to EVAP purge line fitting at EVAP canister. Using scan tool, ensure EVAP canister purge valve is still commanded ON (closed). Attempt to apply vacuum to EVAP canister until FUEL TANK PRESSURE parameter on scan tool reads 1.47-1.51 volts. If FUEL TANK PRESSURE reading is maintained as specified, go to step  8. If FUEL TANK PRESSURE reading can not be maintained as specified, go to step  7.
  6. Check fuel tank vapor and EVAP purge lines for restriction. If restriction is found in either line, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no restriction is found, go to DTC P0452: FUEL TANK PRESSURE SENSOR LOW VOLTAGE  or DTC P0453: FUEL TANK PRESSURE SENSOR HIGH VOLTAGE  .
  7. Check if vent hose is disconnected or damaged. Check EVAP canister for damage. If a problem is found, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem is found, go to step  11.
  8. Check for missing or faulty fuel cap. Check for disconnected or leaking fuel tank vapor line. Check for disconnected or damaged EVAP purge line. If a problem is found, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem is found, go to next step.
  9. Replace EVAP canister purge valve. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM.
  10. Locate and repair cause of no vacuum to EVAP canister purge valve. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM.
  11. Replace EVAP canister cut valve. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM.
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