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Home >> Pontiac >> 2000 >> Firebird Base, 2D Convertible, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Self-Diagnostics - 3.8L >> Diagnostic Tests >> DTC P0440: EVAP System >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. Check for disconnected vacuum or purge lines. Check for loose or missing fuel cap. Check If DTC P0443 or P0449 is also set. Repair as necessary. After repairs, go to next step.
  3. Turn ignition off. Disconnect canister purge line from, EVAP canister purge valve. Turn ignition on, with engine off. Using scan tool, observe FUEL TANK PRESSURE parameter. If scan tool reads zero in. H2O, go to next step. If scan tool does not read zero in. H2O, go to step  20.
  4. Zero pressure and vacuum gauges on EVAP Pressure/Purge Diagnostic Station (J-41413). Turn ignition off. Reinstall previously disconnected components. Install Fuel Fill Cap Adaptor (J-41415-40) between filler neck and fuel cap. Connect EVAP diagnostic station to fuel tank cap adaptor. Turn ignition on, with engine off. Using scan tool, capture FAILURE RECORDS data for this DTC, then clear DTCs. Using scan tool, select SEAL option. Attempt to pressurize EVAP system by slowly turning EVAP diagnostic station rotary switch to PRESSURE position to achieve 5 in. H2O. If specified pressure is achieved, go to next step. If specified pressure is not achieved, to step  6.
  5. Maintain EVAP system pressure at 5 in. H2O. Using scan tool, read FUEL TANK PRESSURE. parameter. If scan tool indicates fuel tank pressure is about 5 in. H2O, go to step  8. If scan tool does not indicate fuel tank pressure is about 5 in. H2O, go to step  7.
  6. Disconnect fuel tank vapor and EVAP purge lines from EVAP canister. Plug fuel tank vapor line fitting at EVAP canister. Connect a hand-held vacuum pump to EVAP purge line fitting at EVAP canister. Ensure EVAP vent solenoid is still commanded ON (closed). Attempt to apply 5 in. Hg vacuum to EVAP canister. If vacuum is maintained as specified, go to step  11. If vacuum cannot be maintained as specified, go to step  10.
  7. Check fuel tank vapor line and EVAP purge line for restriction. If restriction is found, go to step  21. If no restriction is found, go to appropriate DTC P0452 test. See DTC P0452: FUEL TANK PRESSURE SENSOR CIRCUIT LOW VOLTAGE (EXCEPT GRAND PRIX, IMPALA, MONTE CARLO & REGAL)  or DTC P0452: FUEL TANK PRESSURE SENSOR CIRCUIT LOW VOLTAGE (GRAND PRIX, IMPALA, MONTE CARLO & REGAL). .
  8. Maintain fuel tank pressure at 5 in. H2O. Using scan tool, increase purge to 100 percent to relieve system pressure. If pressure decreases to zero in. H2O within 15 seconds, go to next step. If pressure does not decrease to zero in. H2O within 15 seconds, go to step  14.
  9. Connect EVAP pressure/purge diagnostic station vacuum gauge to canister side of purge valve. Start engine. Turn ignition on, with engine off. Using scan tool, select SEAL option to seal EVAP system. Start engine. Run engine speed from 1200-1500 RPM while observing vacuum gauge. If vacuum reading is about zero in. Hg, go to step  18. If vacuum reading is not about 15 in. Hg, go to step  15.
  10. Check if vent hose is disconnected or damaged. Check EVAP canister for damage. Repair as necessary. After repairs, go to step  21. If no problem is found, go to step  17.
  11. Check for disconnected or leaking fuel tank vapor line. Check for disconnected or damaged EVAP purge line. Repair as necessary. After repairs, go to step  21. If no problem is found, go to next step.
  12. Disconnect engine vacuum purge line from EVAP canister purge valve and connect EVAP pressure/purge diagnostic station to canister side of purge valve. Turn ignition on, with engine off. Using scan tool, select SEAL option to seal EVAP system. Start engine. Operate engine from 1200-1500 RPM and observe vacuum level. If vacuum reading is about zero in. Hg, go to next step. If vacuum reading is not about zero in. Hg, go to step  15.
  13. Reconnect all previously disconnected EVAP components. Turn ignition on, with engine off. Using scan tool, seal EVAP system. Using EVAP diagnostic station connected to EVAP service port, continuously attempt to pressurize the EVAP system to, but do not exceed 5 in. H2O by leaving control knob in PRESSURIZE position. Using an Ultrasonic Leak Detector (J-41416), locate and repair leak in EVAP system. After repairs, go to step  21.
  14. Disconnect purge line from canister side of purge valve. If vacuum level on EVAP diagnostic station vacuum gauge is about zero in. Hg, go to next step. If vacuum level on EVAP diagnostic station vacuum gauge is not about zero in. Hg, see DIAGNOSTIC AIDS .
  15. Replace EVAP purge valve. After replacing purge valve, go to step  21.
  16. Check for cause of no vacuum to EVAP purge valve. Repair as necessary. After repairs, go to step  21. If no problem is found, go to step  15.
  17. Replace EVAP vent valve. After replacing vent valve, go to step  21.
  18. Using scan tool, increase purge to 100 percent. Operate engine to 1200-1500 RPM. Observe vacuum level on EVAP diagnostic station vacuum gauge. If vacuum reading is greater than 15 in. Hg, see DIAGNOSTIC AIDS . If vacuum reading is not greater than 15 in. Hg, go to step  16.
  19. Check for kinked or restricted canister purge line between EVAP canister purge valve and canister. Repair as necessary. After repairs, go to step  21.
  20. Turn ignition off. Disconnect EVAP canister line from fuel tank or EVAP canister to relieve fuel tank pressure. Turn ignition on, with engine off. Using scan tool, observe fuel tank pressure parameter. If scan tool indicates that fuel tank pressure is about zero in. H2O, go to step  19. If scan tool indicates that fuel tank pressure is not about zero in. H2O, diagnose using DTC P0453. See DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT HIGH VOLTAGE .
  21. Reconnect all previously disconnected EVAP components. Turn ignition on, engine off. Using scan tool, seal EVAP system. Using EVAP pressure/purge diagnostic station pressurize EVAP system to 15 in. H2O. Monitor EVAP pressure/purge diagnostic station pressure gauge. Turn EVAP pressure/purge diagnostic station rotary switch to HOLD position. If pressure decreases to less than 10 in. H2O within 2 minutes, return to step  3. If pressure does not decrease as specified, system is okay.
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