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Diagnosis & Repair

WARNING: This page is about a different car, the 2002 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
  1. Check for cracks and deformations in fuel tank, charcoal canister and fuel tank filler pipe. Check for disconnected hoses and tubes around fuel tank and charcoal canister. If problem exists, repair as necessary. If problem does not exist, go to next step.
  2. Check fuel tank cap. If fuel tank cap is not an OEM cap, replace fuel tank cap with an OEM cap. If fuel tank cap is an OEM cap, go to next step.
  3. Check if fuel tank cap is properly installed. If problem exists, install fuel tank cap properly. If fuel tank cap is properly installed, go to next step.
  4. Check for damaged fuel tank cap and gasket. If problem exists, replace fuel tank cap with OEM cap. If problem does not exist, go to next step.
  5. Remove fuel tank cap. Visually inspect fuel tank filler neck for damage. If problem exists, replace fuel tank filler neck as necessary. If problem does not exist, go to next step.
  6. Check vacuum hoses between vapor pressure sensor and fuel tank, and between charcoal canister and pressure switching valve VSV. Check hoses for correct installation, looseness and damage. If problem exists, repair vacuum hoses as necessary. If problem does not exist, go to next step.
  7. Check hose and tube between fuel tank and charcoal canister for correct installation and damage. If problem exists, repair as necessary. If problem does not exist, go to next step.
  8. Check all EVAP system electrical component connections. If problem exists, repair as necessary. If problem does not exist, go to next step.
  9. Check vacuum hoses between charcoal canister and fuel tank, and between fuel filler neck and fuel tank. If problem exists, repair as necessary. If problem does not exist, go to next step.
  10. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 18 (Yellow wire) and No. 28 (Brown wire) at ECM harness connector E10. See Figure. Voltage should be 4.5-5.5 volts. If voltage is not as specified, replace ECM. If voltage is as specified, go to next step.
  11. Remove fuel tank cap. Using DVOM, backprobe ECM harness connector and measure voltage between terminal No. 21 (Pink wire) at ECM harness connector E6 and terminal No. 28 (Brown wire) at ECM harness connector E10. Voltage should be 3.0-3.6 volts. See Figure. 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 between vapor pressure sensor and ECM. See WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace vapor pressure sensor.
  13. Disconnect EVAP VSV vacuum hoses. Turn ignition on. Access ECM behind glove box. Connect a jumper wire by backprobing between terminal No. 28 (Brown wire) at ECM connector E10 and terminal No. 11 (Light Green wire) at ECM harness connector E8. See Figure. With jumper wire connected air applied to EVAP VSV port "E" should flow from port "F". See Fig 1. Remove jumper wire. With jumper wire removed, air applied to EVAP VSV port "E" should not flow from port "F". If EVAP VSV functions as specified, go to step  16. If EVAP VSV does not function as specified, go to next step.
  14. Connect all disconnected components. Check EVAP VSV operation. See FUEL EVAPORATIVE SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - ES300 & RX300 article. If EVAP VSV is okay, go to next step. If EVAP VSV is not okay, replace EVAP VSV. Also, clean vacuum hose between throttle body and EVAP VSV, and between EVAP VSV and charcoal canister, then check charcoal canister. See FUEL EVAPORATIVE SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - ES300 & RX300 article.
  15. Check for an open or short in wiring between EFI main relay and EVAP VSV, and between EVAP VSV and ECM. See WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.
  16. Disconnect canister closed valve VSV vacuum hoses. Turn ignition on. Access ECM behind glove box. Connect a jumper wire by backprobing between terminal No. 28 (Brown wire) at ECM connector E10 and terminal No. 12 (Blue wire) at ECM harness connector E8. See Figure. With jumper wire connected air applied to canister closed valve VSV port "E" should not flow from port "F". See Fig 2. Remove jumper wire. With jumper wire removed, air applied to canister closed valve VSV port "E" should flow from port "F". If canister closed valve VSV does not function as specified, go to next step. If canister closed valve VSV functions as specified, go to step  19.
  17. Connect all disconnected components. Check canister closed valve VSV. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - ES300 & RX300 article. If canister closed valve VSV is okay, go to next step. If canister closed valve VSV is defective, replace canister closed valve VSV and charcoal canister. Also, clean vacuum hose between charcoal canister and canister closed valve VSV.
  18. Check for an open or short in wiring between EFI main relay and canister closed valve VSV, and between canister closed valve VSV and ECM. See WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.
  19. Disconnect pressure switching valve VSV vacuum hoses. Turn ignition on. Access ECM behind glove box. Connect a jumper wire by backprobing between terminal No. 28 (Brown wire) at ECM connector E10 and terminal No. 4 (Violet wire) at ECM harness connector E6. See Figure. With jumper wire connected air applied to pressure switching valve VSV port "E" should flow from port "F". See Fig 3. Remove jumper wire. With jumper wire removed, air applied to pressure switching valve VSV port "E" should not flow from port "F". If pressure switching valve VSV functions as specified, go to step  22. If pressure switching valve VSV does not function as specified, go to next step.
  20. Connect all disconnected components. Check pressure switching valve VSV. See FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - ES300 & RX300 article. If pressure switching valve VSV is defective, 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.
  21. Check for an open or short in wiring between EFI main relay and pressure switching valve VSV, and between pressure switching valve VSV and ECM. See WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.
  22. Connect all disconnected components. Charcoal canister or fuel tank overfill check valve maybe defective. Check fuel evaporative system. See FUEL EVAPORATIVE SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - ES300 & RX300 article. Repair as necessary. If no problem is indicated, replace ECM.
Fig 1: Identifying EVAP VSV Vacuum Ports
G96D09634Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Fig 2: Identifying Canister Closed Valve VSV Vacuum Ports
G00131746Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Fig 3: Identifying Pressure Switching Valve VSV Vacuum Ports
G99A52753Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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