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Home >> Lexus >> 1999 >> ES 300 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics - Tests >> Diagnostic Tests >> DTC P0441: Incorrect EVAP Purge Flow Or DTC P0446: EVAP Vent Control Fault >> Diagnosis & Repair (Using Lexus Scan Tool)

Diagnosis & Repair (Using Lexus Scan Tool)

  1. Check EVAP VSV, vapor pressure sensor VSV and vapor pressure sensor wiring harness connectors for damaged pins, corrosion and loose wires. Repair as necessary. If connectors are okay, go to next step. For component locations, see appropriate illustration in THEORY & OPERATION article.
  2. Check all EVAP related vacuum hoses for damage, blockage, looseness and correct routing. Repair as necessary. If vacuum hoses are okay, go to next step. For proper vacuum hose routing, see appropriate illustration in VACUUM DIAGRAMS article.
  3. Access ECM harness connectors behind glove box. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals No. 2 (Yellow wire) and No. 18 (Brown wire) at ECM E10 connector. See Figure. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, replace ECM and retest system.
  4. Backprobing ECM harness connector, measure voltage between terminal No. 17 (Pink wire) at ECM E7 connector and terminal No. 18 (Brown wire) at ECM E10 connector. Disconnect vacuum hose from vapor pressure sensor. Sensor has 2 vacuum ports and is located on charcoal canister underneath rear of vehicle. See Figure. Connect a vacuum pump to sensor. Voltage should be 2.9-3.7 volts without vacuum applied, and .5 volt or less with 1.2-19.7 in. Hg (4-66 kPa) applied. If voltage is as specified, go to step  6. If voltage is not as specified, go to next step.
  5. Check for an open or short in wiring harness between vapor pressure sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace vapor pressure sensor.
  6. Connect scan tool to Data Link Connector (DLC) No. 3. See Figure Using scan tool, select ACTIVE TEST mode. Disconnect EVAP VSV vacuum hose from charcoal canister. Start engine. Connect a vacuum gauge to disconnected vacuum hose. Using scan tool, activate EVAP VSV. When EVAP VSV is activated, vacuum should be present. When EVAP VSV is not activated, no vacuum should be present. If vacuum is as specified, go to step  10. If vacuum is not as specified, go to next step.
  7. Check for correct routing, looseness, damage and blockage in vacuum hoses between intake manifold and EVAP VSV, and between EVAP VSV and charcoal canister. Repair as necessary. If hoses are okay, go to next step.
  8. Check EVAP VSV. See appropriate SYSTEM & COMPONENT TESTING article. If EVAP VSV is not okay, replace EVAP VSV and charcoal canister. Also clean vacuum hoses between throttle body and EVAP VSV, and EVAP VSV and charcoal canister. If EVAP VSV is okay, go to next step.
  9. Check for an open or short in wiring harness between EFI main relay, EVAP VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest system.
  10. Disconnect vapor pressure sensor VSV. Sensor has 3 vacuum ports and is located on charcoal canister underneath rear of vehicle. See Figure. Connect scan tool to Data Link Connector (DLC) No. 3. See Figure. Turn ignition on. Select ACTIVE TEST mode on scan tool. Using scan tool, turn vapor pressure sensor VSV on. Apply compressed air to port "E" of vapor pressure sensor VSV. Air should flow from port "F". See Fig 1. Using scan tool, turn vapor pressure sensor VSV off. Air should flow from port "G". If valve operates correctly, go to step  13. If valve does not operate correctly, go to next step.
  11. Check vapor pressure sensor VSV. See appropriate SYSTEM & COMPONENT TESTING article. If vapor pressure sensor VSV is not okay, replace vapor pressure sensor VSV and charcoal canister. Also clean vacuum hoses between charcoal canister and vapor pressure sensor VSV, and vapor pressure sensor VSV and vapor pressure sensor. If vapor pressure sensor VSV is okay, go to next step.
  12. Check for an open or short in wiring harness between EFI main relay, vapor pressure sensor VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest system.
  13. Connect scan tool to Data Link Connector (DLC) No. 3. See Figure Select ACTIVE TEST mode on scan tool. Ensure vapor pressure sensor VSV is disconnected. Start engine. Using scan tool, activate EVAP VSV. Backprobing ECM harness connector, measure voltage between terminal No. 17 (Pink wire) at ECM E7 connector and terminal No. 18 (Brown wire) at ECM E10 connector. See Figure. Voltage should be 2 volts or less. If voltage is as specified, go to step  15. If voltage is not as specified, go to next step.
  14. Check vacuum hose between charcoal canister and vapor pressure sensor VSV, and vacuum hose between vapor pressure sensor and vapor pressure sensor VSV. If problem exists, repair vacuum hoses as necessary. If problem does not exist, go to next step.
  15. Remove fuel tank cap. Ensure vapor pressure sensor VSV connector is disconnected. Select ACTIVE TEST mode on scan tool. Start engine. Using scan tool, switch EVAP VSV on for 5 seconds. Backprobing ECM harness connector, measure voltage between terminals No. 17 (Pink wire) at ECM E7 connector and No. 18 (Brown wire) at ECM E10 connector 5 seconds after switching EVAP VSV from on to off. If voltage is 2.5 volts or less, go to next step. If voltage is more than 2.5 volts, replace charcoal canister.
  16. Charcoal canister or fuel tank overfill check valve maybe defective. Check fuel evaporation system. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. Repair as necessary. If no problem is indicated, replace ECM.
Fig 1: Identifying Vapor Pressure Sensor VSV Vacuum Ports
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