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Diagnosis & Repair (Using Lexus Scan Tool)

WARNING: This page is about a different car, the 2002 Lexus RX 300. However, it is still accessible from the selected car via links, so may be relevant.
  1. Check for cracks, deformations or loose connections in following:
    • Fuel tank.
    • Charcoal canister.
    • Fuel tank filler pipe.
    • Hose and tubes around fuel tank and charcoal canister.

    Repair as necessary. If components are okay, go to next step.

  2. Check if fuel tank cap is an original manufacturer's cap. If fuel tank cap is an original manufacturer's cap, go to next step. If fuel tank cap is not an original manufacturer cap, replace cap with a manufacturer's cap.
  3. Check if fuel cap is installed properly. Reinstall cap as necessary. If fuel cap is installed properly, go to next step.
  4. Check for damaged fuel tank cap and gasket. Replace fuel tank cap as necessary. If fuel tank cap and gasket are okay, go to next step.
  5. Remove fuel tank cap. Visually inspect fuel tank filler neck for damage. Replace filler neck as necessary. If filler neck is okay, go to next step.
  6. Check vacuum hoses between vapor pressure sensor and fuel tank, and between pressure switching valve VSV and charcoal canister. Check hoses for correct installation, looseness and damage. Repair as necessary. If vacuum hoses are okay, go to next step.
  7. Check hose and tube between fuel tank and charcoal canister for correct installation and damage. Repair as necessary. If hose and tube are okay, go to next step.
  8. Check EVAP VSV, canister closed valve VSV, pressure switching valve 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 Figure.
  9. Check all EVAP related vacuum hoses between fuel tank and charcoal canister, and between fuel tank and fuel tank overfill check valve 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 Figure.
  10. Access ECM harness connectors behind glove box. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals No. 2 (Yellow/Black wire) and No. 18 (Brown wire) at ECM E8 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.
    NOTE: DO NOT apply more than 19.7 in. Hg (66.7 kPa) to vapor pressure sensor.
  11. Locate vapor pressure sensor on top of fuel tank. See Figure. Leaving harness connector attached, remove vapor pressure sensor from top of fuel tank. See Figure. Backprobing ECM harness connectors, connect voltmeter between terminal No. 17 (Blue/Orange wire) at ECM E5 connector and terminal No. 18 (Brown wire) at ECM E8 connector. See Figure. Connect a vacuum pump to vapor port on sensor. Voltage should be 2.9-3.7 volts without vacuum applied, and .5 volts or less with 1.18 in. Hg (4.0 kPa) applied. If voltage is as specified, go to step  13. If voltage is not as specified, go to next step.
  12. Check for an open or short in wiring harness between vapor pressure sensor and ECM. See WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace vapor pressure sensor.
  13. Connect scan tool to Data Link Connector (DLC) No. 3. See Figure. Using scan tool, select ACTIVE TEST mode. Disconnect vacuum hose from charcoal canister at EVAP VSV. See Figure. 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  17. If vacuum is not as specified, go to next step.
  14. 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.
  15. Check EVAP VSV. See SYSTEM & COMPONENT TESTING - ES300 & RX300 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.
  16. Check for an open or short in wiring harness between EFI main relay, EVAP VSV and ECM. See WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest system.
  17. Turn ignition off. Disconnect closed canister valve VSV vacuum hose. VSV is mounted on or near air filter housing. 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 canister closed valve VSV on. Apply compressed air to port "B" of canister closed valve VSV. Air should not flow from port "A". See Fig 1. Using scan tool, turn canister closed valve VSV off. Air should flow from port "A". If VSV operates correctly, go to step  21. If VSV does not operate correctly, go to next step.
    Fig 1: Identifying Canister Closed Valve VSV Vacuum Ports
    G99D52749Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  18. Check for correct routing, looseness, damage and blockage in vacuum hoses between canister closed valve VSV and charcoal canister. Repair as necessary. If hose is okay, go to next step.
  19. Check canister closed valve VSV. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING article. If canister closed valve VSV is not okay, replace canister closed valve VSV and charcoal canister. Also clean vacuum hoses between charcoal canister and canister closed valve VSV. If canister closed valve VSV is okay, go to next step.
  20. Check for an open or short in wiring harness between EFI main relay, canister closed valve VSV and ECM. See WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest system.
  21. Connect scan tool to Data Link Connector (DLC) No. 3. See Figure. Ensure ignition is on. Select ACTIVE TEST mode on scan tool. Locate pressure switching valve VSV on charcoal canister. See Figure. Disconnect vacuum hoses from pressure switching valve VSV. Using scan tool, activate pressure switching valve VSV. Apply compressed air to port "E" of pressure switching valve VSV. Air should flow from port "F". See Fig 2. Using scan tool, turn pressure switching valve VSV off. Air should not flow from port "F". If VSV operates correctly, go to step  24. If VSV does not operate correctly, go to next step.
    Fig 2: Identifying Pressure Switching Valve VSV Vacuum Ports
    G00024240Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  22. Check pressure switching valve VSV. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. If pressure switching valve VSV is not okay, replace pressure switching valve VSV and charcoal canister. Also clean vacuum hose between charcoal canister and pressure switching valve VSV, and between pressure switching valve VSV and fuel tank. If pressure switching valve VSV is okay, go to next step.
  23. Check for an open or short in wiring harness between EFI main relay, pressure switching valve VSV and ECM. See WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest system.
  24. Access ECM behind glove box. Backprobing ECM harness connector, connect DVOM between terminal No. 17 (Blue/Orange wire) at ECM E5 connector and terminal No. 18 (Brown wire) at ECM E8 connector. See Figure. Select ACTIVE TEST mode on scan tool. Start engine. EVAP VSV, canister closed valve VSV and pressure switching valve VSV should all be on. Observing DVOM, when voltage reaches 1.2 volts, switch EVAP VSV and pressure switching valve VSV off. See Fig 3. Wait 30 seconds and note DVOM voltage reading. If voltage stays at 1.2 volts, fuel tank is okay. Go to next step. If voltage does not stay at 1.2 volts, replace fuel tank.
    Fig 3: Checking Fuel Tank By Measuring PTNK Circuit Voltage At ECM
    G99C52755Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  25. Access ECM behind glove box. Backprobing ECM harness connector, connect DVOM between terminal No. 17 (Blue/Orange wire) at ECM E5 connector and terminal No. 18 (Brown wire) at ECM E8 connector. See Figure. Select ACTIVE TEST mode on scan tool. Start engine. EVAP VSV, canister closed valve VSV and pressure switching valve VSV should all be on. Observing DVOM, when voltage reaches 1.2 volts, switch EVAP VSV off. See Fig 4. Wait 30 seconds and note DVOM voltage reading. If voltage stays at 1.2 volts, go to next step. If voltage does not stay at 1.2 volts, replace charcoal canister.
    Fig 4: Checking Charcoal Canister By Measuring PTNK Circuit Voltage At ECM
    G99E52757Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  26. Charcoal canister or fuel tank overfill check valve may be 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.
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