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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 P0446: EVAP Vent System Performance >> 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 fill cap. Check if DTC P0443 or P0449 are set. Repair as necessary. If no problem is found, go to next step.
  3. 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 fuel tank pressure is about zero in. H2O, go to next step. If fuel tank pressure is not about zero in. H2O, go to step  11.
  4. Zero pressure and vacuum gauges on EVAP Pressure/Purge Diagnostic Station (J-41413). Reconnect previously disconnected components. Install Fuel Fill Cap Adaptor between fuel filler neck and fill cap. Turn ignition on, with engine off. Using scan tool, capture FAIL RECORDS data for this DTC. Clear DTC. Using scan tool, command vent valve on (closed) to seal system. Using EVAP pressure/purge diagnostic station, attempt pressurize EVAP system to 5 in. H2O. Using scan tool, read FUEL TANK PRESSURE. If scan tool indicates that fuel tank pressure is 5 in. H2O, go to next step. If scan tool does not indicate that fuel tank pressure is 5 in. H2O, go to step  7.
  5. Maintain EVAP system pressure at 5 in. H2O. Using scan tool, command EVAP vent solenoid OFF (open). Monitor EVAP pressure/purge diagnostic station pressure gauge. If pressure decreases to zero in. H2O within 2 minutes, see DIAGNOSTIC AIDS . If pressure does not decrease to zero in. H2O within 2 minutes, go to next step.
  6. Disconnect vent hose, marked AIR, from EVAP canister. Switch EVAP pressure/purge diagnostic station rotary switch to PURGE. Warm engine to normal operating temperature. Monitor vacuum gauge for 5 seconds while holding engine speed at 2500 RPM. If vacuum remains at less than 10 in. H2O, go to next step. If vacuum does not remain at less than 10 in. H2O, go to step  9.
  7. Check if vent hose is between EVAP canister and EVAP solenoid is kinked, pinched or blocked. Repair as necessary. After repairs, go to step  12. If no problem is found, go to next step.
  8. Replace EVAP vent solenoid. After replacing solenoid, go to step  12.
  9. Replace EVAP canister. After replacing canister, go to step  12.
  10. Check for kinked or restricted canister purge line between EVAP canister purge valve and canister. Repair as necessary. After repairs, go to step  12.
  11. Turn ignition off. Disconnect EVAP canister line from fuel tank or EVAP canister. Turn ignition on, with engine off. Using scan tool, observe fuel tank pressure parameter. If fuel tank pressure is about zero in. H2O, go to step  10. If fuel tank pressure is not about zero in. H2O, diagnose using DTC P0453 test. See DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT HIGH VOLTAGE .
  12. Reconnect all previously disconnected EVAP components. Turn ignition on, with engine off. Using scan tool, command EVAP vent solenoid ON (closed) to seal system. Using EVAP diagnostic station connected to EVAP service port, pressurize EVAP system to 5 in. H2O. Switch EVAP pressure/purge diagnostic station rotary switch to HOLD. Using scan tool, command EVAP vent solenoid OFF (open). If pressure decreases to zero in. H2O within 2 minutes, go to step  3. If pressure does not decrease to zero in. H2O within 2 minutes, system is okay.
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