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Home >> Lexus >> 1999 >> SC 300 >> Repair and Diagnosis (Single Page) >> 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 for loose or disconnected connectors at EVAP VSV, vapor pressure sensor VSV and vapor pressure sensor. Repair as necessary. If all connectors are okay, go to next step.
  2. Check for correct routing, damage, looseness and blockage in vacuum hoses between vapor pressure sensor and vapor pressure sensor VSV, and between vapor pressure sensor VSV and charcoal canister. Also check vacuum hoses between EVAP VSV and charcoal canister, between EVAP VSV and air resonator, and between intake manifold and charcoal canister. Repair as necessary. If vacuum hoses are okay, go to next step.
  3. Turn ignition on. Backprobing, measure voltage between terminals No. 2 (Blue/Black wire) and No. 18 (Brown wire) at ECM E16 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, measure voltage between terminals No. 18 (Red wire) at ECM E18 connector and No. 18 (Brown wire) at ECM E16 connector. See Figure. Disconnect vacuum hose from vapor pressure sensor. Vapor pressure sensor is a 2-port sensor that is mounted on top of charcoal canister. Canister is located at right front of vehicle. Connect a vacuum pump to sensor. If voltage is 2.9-3.7 volts without vacuum applied, and .5 volt or less with 1.2-19.7 in. Hg applied, go to step  6. If voltage is not as specified, go to next step.
  5. Check for an open or short circuit in wiring harness and connector between vapor pressure sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring harness and connector are okay, replace vapor pressure sensor and retest.
  6. Connect Lexus 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. See Figure. Start and run engine.
  7. Connect vacuum gauge to disconnected EVAP VSV vacuum hose. Check for vacuum at vacuum hose when EVAP VSV is activated by scan tool. Vacuum should exist with EVAP VSV switched on. Vacuum should not exist with EVAP VSV switched off. If EVAP VSV operates as specified, go to step  12. If EVAP VSV does not operate as specified, go to next step.
  8. Check for correct routing, damage, looseness and blockage in vacuum hoses between throttle body and EVAP VSV, and between EVAP VSV and charcoal canister. Repair as necessary. If vacuum hoses are okay, go to next step.
  9. Remove EVAP VSV. Using ohmmeter, measure resistance between EVAP VSV terminals. With EVAP VSV temperature at 68°F (20°C), resistance should be 27-33 ohms. Measure resistance between each terminal and body of valve. Resistance should be infinite. If resistance is as specified, go to next step. If resistance is not as specified, replace EVAP VSV and charcoal canister. After replacing components, clean vacuum hoses between throttle body and EVAP VSV, and between EVAP VSV and charcoal canister.
  10. Using fused jumper wires, apply battery voltage and ground to EVAP VSV terminals. Apply compressed air to EVAP VSV port "E". Air should flow from port "F". See Figure. Disconnect fused jumper wires. Air should not flow from port "F". If EVAP VSV does not operate as specified, replace EVAP VSV and charcoal canister. After replacing components, clean vacuum hoses between EVAP VSV and throttle body, and between EVAP VSV and charcoal canister. If EVAP VSV operates as specified, go to next step.
  11. Check for open or short circuit in wiring harness and connector between EFI main relay, EVAP VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring harness and connector are okay, replace ECM and retest.
  12. Turn ignition on. Turn Lexus scan tool on. Using scan tool, select ACTIVE TEST mode. Disconnect vapor pressure sensor VSV vacuum hose from charcoal canister. See Figure. Using scan tool turn vapor pressure sensor VSV on. Apply air pressure to VSV port "E". Air should flow from port "F". Using scan tool turn vapor pressure sensor VSV off. Air should flow from port "G". If vapor pressure sensor VSV does not operate as specified, go to next step. If vapor pressure sensor VSV operates as specified, go to step  16.
  13. Remove vapor pressure sensor VSV. Using ohmmeter, measure resistance between vapor pressure sensor VSV terminals. With vapor pressure sensor VSV temperature at 68°F (20°C), resistance should be 37-44 ohms. Measure resistance between each terminal and body of valve. Resistance should be infinite. If resistance is as specified, go to next step. If resistance is not as specified, replace vapor pressure sensor VSV and charcoal canister. After replacing components, clean vacuum hoses between vapor pressure sensor VSV and vapor pressure sensor, and between vapor pressure sensor VSV and charcoal canister.
  14. Using fused jumper wires, apply battery voltage and ground to vapor pressure sensor VSV terminals. Apply compressed air to vapor pressure sensor VSV port "E". Air should flow from port "F". See Figure. Disconnect fused jumper wires. Air should flow from port "G". If vapor pressure sensor VSV does not operate as specified, replace vapor pressure sensor VSV and charcoal canister. After replacing components, clean vacuum hoses between vapor pressure sensor VSV and vapor pressure sensor, and between vapor pressure sensor VSV and charcoal canister. If vapor pressure sensor VSV operates as specified, go to next step.
  15. Check for open or short circuit in wiring harness and connector between EFI main relay, vapor pressure sensor VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring harness is okay, replace ECM and retest.
  16. Connect Lexus scan tool to Data Link Connector (DLC) No. 3. See Figure. Disconnect vapor pressure sensor VSV harness connector. Using scan tool, select ACTIVE TEST mode. Start and run engine. Using scan tool, turn EVAP VSV on. Access ECM under front of carpet on passenger side of vehicle. Backprobing, measure voltage between terminal No. 18 (Red wire) at ECM E18 connector and terminal No. 18 (Brown wire) at ECM E16 connector . See Figure. If voltage is more than 2 volts, go to next step. If voltage is 2 volts or less, go to step  18.
  17. Check for correct routing, damage, looseness and blockage in vacuum hoses between charcoal canister and vapor pressure sensor VSV, and between vapor pressure sensor VSV and vapor pressure sensor. Repair as necessary. If vacuum hoses are okay, go to next step.
  18. Remove fuel cap. Disconnect vapor pressure sensor VSV. Using scan tool, select ACTIVE TEST mode. Start and run engine. Backprobing, measure voltage between terminal No. 18 (Red wire) at ECM E18 connector and terminal No. 18 (Brown wire) at ECM E16 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 or less, replace charcoal canister.
  19. Remove charcoal canister. Visually inspect charcoal canister for cracks or damage. Close port "B". See Figure. Apply .26 psi (.02 kg/cm2 ) of compressed air to port "A" of charcoal canister. Air should flow from port "D".
  20. Close ports "B" and "D". See Figure. Apply .26 psi (.02 kg/cm2 ) of compressed air to port "A" of charcoal canister. Air should not flow from port "C".
  21. Apply 1.01 in. Hg. (3.43 kPa) of vacuum to port "B". See Figure. Vacuum should not decrease with port "C" closed and should decrease with port "C" open.
  22. Close port "C". Connect vacuum gauge port "B". Apply .29 in. Hg. (.98 kPa) of vacuum to port "A". Vacuum should exist at port "B". If charcoal canister does not operate as specified, replace charcoal canister. If charcoal canister operates as specified, replace ECM and retest.
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