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Home >> Lexus >> 2000 >> LX 470 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0441: Incorrect EVAP Purge Flow Or DTC P0446: EVAP Vent Control Circuit >> Diagnosis & Repair (Using Lexus Scan Tool)

Diagnosis & Repair (Using Lexus Scan Tool)

  1. Check EVAP VSV, vapor pressure sensor VSV and vapor pressure sensor harness connectors for damaged pins, corrosion and loose wires. If problem exists, repair connectors as necessary. If problem does not exist, go to next step.
  2. Check all EVAP related vacuum hoses for cracks, looseness and correct routing. For proper vacuum hose routing, see appropriate illustration in VACUUM DIAGRAMS article. If problem exists, repair vacuum hoses as necessary. If problem does not exist, go to next step.
  3. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 2 (Blue/Red wire) and No. 18 (Brown/White wire) at ECM harness connector E7. See Figure. If voltage is not 4.5-5.5 volts, replace ECM. If voltage is 4.5-5.5 volts, go to next step.
  4. Using DVOM, backprobe ECM harness connector and measure voltage between terminal No. 22 (Blue/Black wire) at ECM harness connector E8 and terminal No. 18 (Brown/White wire) at ECM harness connector E7. See Figure. Disconnect vacuum hose from vapor pressure sensor. Connect a vacuum pump to vapor pressure sensor. Voltage should be 2.9-3.7 volts without vacuum applied and .5 volt or less with 1.18 in. Hg 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 between vapor pressure sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace vapor pressure sensor.
  6. Connect scan tool to Data Link Connector (DLC) No. 3. See Figure. Turn ignition on. Using scan tool, select ACTIVE TEST mode. Disconnect vacuum hose from port "B" (purge port) at charcoal canister. See Fig 1. Start engine. Connect a vacuum gauge to disconnected vacuum hose. When EVAP VSV is activated by scan tool, vacuum should exist. When EVAP VSV is not activated, vacuum should not exist. If vacuum is as specified, go to step  10. If vacuum is not as specified, go to next step.
  7. Check vacuum hose between intake manifold and EVAP VSV, and vacuum hose between EVAP VSV and charcoal canister. If problem exists, replace vacuum hoses as necessary. If problem does not exist, go to next step.
  8. Check EVAP VSV operation. See EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace EVAP VSV. If problem does not exist, go to next step.
  9. Check for an open or short in wiring between EFI main relay, EVAP VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.
  10. Turn ignition on. Using scan tool, select ACTIVE TEST mode. Disconnect vacuum hoses from vapor pressure sensor VSV. Apply air pressure to vapor pressure sensor VSV port "E". See Fig 2. When vapor pressure sensor VSV is activated by scan tool, air should flow from port "F". When vapor pressure sensor VSV is not activated, air should flow from port "G". If vapor pressure sensor VSV operates as specified, go to step  13. If vapor pressure sensor VSV does not operate as specified, go to next step.
  11. Check vapor pressure sensor VSV. See EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, replace vapor pressure sensor VSV. If problem does not exist, go to next step.
  12. Check for open or short in wiring between EFI main relay, vapor pressure sensor VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.
  13. Disconnect vapor pressure sensor VSV harness connector. Start engine. Using scan tool, select ACTIVE TEST mode. Using DVOM, backprobe ECM harness connector and measure voltage between terminal No. 22 (Blue/Black wire) at ECM harness connector E9 and terminal No. 18 (Brown/White wire) at ECM harness connector E8. See Figure. With EVAP VSV activated by scan tool, 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 cap. Disconnect vapor pressure sensor VSV harness connector. Using scan tool, select ACTIVE TEST mode. Start engine. Using DVOM, backprobe ECM harness connector and measure voltage between terminal No. 22 (Blue/Black wire) at ECM harness connector E9 and terminal No. 18 (Brown/White wire) at ECM harness connector E7 5 seconds after switching EVAP VSV from on to off. If voltage is 2.5 volts or less, replace charcoal canister. If voltage is more than 2.5 volts, go to next step.
  16. Perform appropriate fuel EVAP system test. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. If problem exists, repair as necessary. If problem does not exist, replace ECM.
Fig 1: Identifying Charcoal Canister Ports
G98I12490Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Fig 2: Identifying Vapor Pressure Sensor Vacuum Switching Valve (VSV) Ports
G96A10199Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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