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Diagnosis & Repair (Using Toyota Scan Tool)

  1. Check EVAP VSV, vapor pressure sensor 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 appropriate illustration in THEORY/OPERATION article.
  2. Check all EVAP related vacuum hoses for cracks, looseness and correct routing. Replace vacuum hoses as necessary. If vacuum hoses are okay, go to next step. For proper vacuum hose routing, see appropriate illustration in VACUUM DIAGRAMS article.
  3. Access ECM behind bottom center of instrument panel, in front of console. Turn ignition on. Backprobing ECM connector, measure voltage between terminals No. 1 (Yellow wire) and No. 9 (Brown wire) at ECM E5 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.
  4. Backprobing ECM connector, measure voltage between terminals No. 7 (Blue/Yellow wire) and No. 9 (Brown wire) at ECM E5 connector. Disconnect vacuum hose from vapor pressure sensor. Sensor is located near brake master cylinder. Apply vacuum or pressure to sensor as specified. Voltage reading should be as follows:
    • 2.9-3.7 volts with no vacuum applied.
    • 4.2-4.8 volts with .22 psi (1.5 kPa) pressure applied.
    • 1.3-2.1 volts with .59 in. Hg (2.0 kPa) vacuum applied.

    If voltage is as specified, go to step 6). If voltage is not as specified, go to next step.

  5. Check for open or short circuit in wiring harness between vapor pressure sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring as necessary. If wiring harness is okay, replace vapor pressure sensor.
  6. Connect scan tool to DLC No. 3. Turn ignition on. Using scan tool, select ACTIVE TEST mode. Disconnect EVAP VSV vacuum hose from charcoal canister. Start engine. Connect a vacuum gauge to disconnected vacuum hose. When EVAP VSV is activated by scan tool, vacuum should be present. When EVAP VSV is not activated, no vacuum should be present. If vacuum is as specified, go to step 9). If vacuum is not as specified, go to next step.
  7. Check EVAP VSV. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS article. Replace VSV as necessary. If VSV is okay, go to next step.
  8. Check for open or short circuit in wiring harness between EFI main relay, EVAP VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring as necessary. If wiring harness is okay, replace ECM and retest.
  9. Connect scan tool to DLC No. 3. See Figure. Turn ignition on. Disconnect vapor pressure sensor VSV connector. VSV is mounted on top of EVAP charcoal canister. Start and run engine. Using scan tool, select ACTIVE TEST mode. Backprobing ECM connector, measure voltage between terminals No. 7 (Blue/Yellow wire) and No. 9 (Brown wire) at ECM E5 connector. See Figure. With EVAP VSV activated, voltage should be 2.5 volts or less. If voltage is as specified, go to step 11). If voltage is not as specified, go to next step.
  10. Check vacuum hose between charcoal canister and vapor pressure sensor VSV. Also check vacuum hose between vapor pressure sensor and vapor pressure sensor VSV. Replace vacuum hoses as necessary and retest. If vacuum hoses are okay, go to next step.
  11. Check vapor pressure sensor VSV. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS article. Replace VSV as necessary. If VSV is okay, go to next step.
  12. Check for open or short circuit in wiring harness between EFI main relay, vapor pressure sensor VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring as necessary. If wiring harness is okay, go to next step.
  13. Remove fuel tank cap. Disconnect vapor pressure sensor VSV connector. Using scan tool, select ACTIVE TEST mode. Start engine. Using scan tool, switch EVAP VSV on. Backprobing ECM connector, measure voltage between terminals No. 7 (Blue/Yellow wire) and No. 9 (Brown wire) at ECM E5 connector 5 seconds after switching EVAP VSV from on to off. If voltage is 2.5 volts or less, replace ECM and retest. If voltage is more than 2.5 volts, replace charcoal canister.
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