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Diagnosis & Repair (Using OBD-II Scan Tool)

WARNING: This page is about a different car, the 2003 Lexus LX 470. However, it is still accessible from the selected car via links, so may be relevant.
  1. Check that fuel tank cap is LEXUS genuine parts. Repair as necessary. If okay, go to next step.
  2. Check that fuel tank cap is correctly installed. Repair as necessary. If okay, go to next step.
  3. Check fuel tank cap. Repair as necessary. If okay, go to next step.
  4. Check filler neck for damage. Repair as necessary. If okay, go to next step.
  5. Check whether hose close to fuel tank has been modified, and check whether there are signs of any accident near fuel tank or charcoal canister. Repair or replace as necessary. If okay, go to next step.
  6. Check vacuum hoses between vapor pressure sensor and fuel tank, charcoal canister and VSV for pressure switching valve, and VSV for pressure switching valve and charcoal canister. See Figure. Repair or connect VSV or sensor connector as necessary. If okay, go to next step.
  7. Check hose and tube between fuel tank and charcoal canister. Repair as necessary. If okay, go to next step.
  8. Check VSV connector for EVAP, VSV connector for CCV, VSV connector for pressure switching valve and vapor pressure sensor connector for looseness and disconnection. Repair or connect VSV or sensor connector. If okay, go to next step.
  9. Check vacuum hoses No. 8 and 9. See Figure. Repair or replace as necessary. If okay, go to next step.
  10. Remove the glove compartment door. Turn the ignition switch ON. Measure the voltage between terminals VC and E2 of the ECM 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.
  11. Measure the voltage between terminals PTNK and E2 of the ECM connectors. Disconnect the vacuum hose from the vapor pressure sensor. Using the MITYVAC (hand-held vacuum pump) apply a vacuum of 1.18 in. Hg (30 mm Hg) to the vapor pressure sensor. The vacuum applied to the vapor pressure sensor must be less than 19.7 in. Hg (500 mm Hg). See Figure. If voltage is 2.9-3.7 volts with vacuum hose disconnected, then changes to 0.5 volt or less, go to step  13. If voltage is not to specification, go to next step.
  12. Check for open and short in harness and connector between vapor pressure sensor and ECM. Repair or replace as necessary. If okay, replace vapor pressure sensor.
  13. Connect jumper wire between terminal PRG of the ECM connector and body ground, then disconnect wire. When VSV is ON, air from port "E" flows out through port "F". When VSV is OFF, air does not flow from port "E" to port "F". See Fig 1. If okay, go to step  16. If not okay, go to next step.
    Fig 1: Checking VSV For EVAP
    G00239885Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  14. Check operation of VSV for EVAP. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - LX470 article. If okay, go to next step. If not okay, replace VSV and clean vacuum hoses between throttle body and VSV for EVAP, and VSV for EVAP and charcoal canister, and then check charcoal canister.
  15. Check for open and short in harness and connector between EFI or ECD relay and VSV for EVAP, and VSV for EVAP and ECM. Repair or replace as necessary. If okay, check and replace ECM.
  16. Connect jumper wire between terminal CCV of the ECM connector and body ground, then disconnect jumper wire. See . When VSV is ON, air does not flow from port "E" to port "F". When VSV is OFF, air from port "E" flows out through port "F". See Fig 2. If okay, go to step  19. If not okay, go to next step.
    Fig 2: Locating ECM Connector Terminal CCV & Checking VSV For CCV
    G00239886Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  17. Check operation of VSV for CCV. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - LX470 article. If okay, go to next step. If not okay, replace VSV and charcoal canister, and then clean vacuum hose between charcoal canister and VSV for CCV.
  18. Check for open and short in harness and connector between EFI or ECD relay and VSV for CCV, and VSV for CCV and ECM. Repair as necessary. If okay, check and replace ECM.
  19. Connect jumper wire between terminal TBP of the ECM connector and body ground, then disconnect wire. When VSV is ON, air from port "E" flows out through port "F". When VSV is OFF, air does not from flow port "E" to port "F". See Fig 3. If okay, check and replace charcoal canister. If not okay, go to next step.
    Fig 3: Checking VSV For Pressure Switching Valve & Locating ECM Connector Terminal TBP
    G00239887Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  20. Check operation of VSV for pressure switching valve. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - LX470 article. If okay, go to next step. If not okay, replace VSV and charcoal canister, and then clean vacuum hoses between charcoal canister and VSV for pressure switching valve, and VSV for pressure switching valve and fuel tank.
  21. Check for open and short in harness and connector between EFI or ECD relay and VSV for pressure switching valve, and VSV for pressure switching valve, and VSV for pressure switching valve and ECM. Repair or replace harness or connector as necessary. If okay, check and replace ECM.
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