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Diagnosis & Repair (Using OBD-II 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 glove box. Turn ignition on. Backprobing ECM connector, measure voltage between terminals No. 11 (Light Green/Red wire) and No. 9 (Brown wire) at ECM E6 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. Backprobe ECM connector. Measure voltage between terminals No. 12 (Yellow/Black wire) and No. 9 (Brown wire) at ECM E6 connector. Disconnect vacuum hose from vapor pressure sensor. Sensor is located in right rear of engine compartment. Connect a vacuum pump to sensor. If voltage is 2.9-3.7 volts without vacuum applied and 1.3-2.1 volts with .59 in. Hg (2 kPa) applied, 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. Access ECM behind glove box. Turn ignition on. Connect a jumper wire between ground and terminal No. 7 (Blue/White wire) at ECM E6 connector. With jumper wire connected EVAP Vacuum Switching Valve (VSV) is on. Apply air pressure to VSV port "E". Air from port "E" should flow from port "F". See Figure. Disconnect jumper wire. Air from port "E" should not flow from port "F". If VSV operates as specified, go to step 10). If VSV does not operate as specified, go to next step.
  7. Remove EVAP VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 30-34 ohms at 68°F (20°C). Measure resistance between each terminal and body of VSV. Resistance should be infinite. If resistance is not as specified, replace VSV. If resistance is as specified, go to next step.
  8. Check VSV operation. Apply battery voltage to VSV terminals. Apply air pressure to VSV port "E". See Figure. Air from port "E" should flow from port "F". Remove battery voltage from VSV terminals. Air from port "E" should not flow from port "F". Replace VSV as necessary. If VSV operates as specified, go to next step.
  9. Check for open or short circuit in wiring harness between 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.
  10. Access ECM behind glove box. Turn ignition on. Connect a jumper wire between ground and terminal No. 8 (Gray/Yellow wire) at ECM E6 connector. With jumper wire connected vapor pressure sensor Vacuum Switching Valve (VSV) is on. Apply air pressure to VSV port "E". See Figure. Air from port "E" should flow from port "F". Disconnect jumper wire. Air from port "E" should flow from port "G". If VSV operates as specified, check charcoal canister. See SYSTEM/COMPONENT TESTS article. If VSV does not operate as specified, go to next step.
  11. Disconnect vapor pressure sensor VSV vacuum hoses. VSV is mounted near right shock tower. Using ohmmeter, measure resistance between VSV terminals. If resistance is 33-39 ohms at 68°F (20°C), go to next step. If resistance is not 33-39 ohms, replace VSV.
  12. Check for continuity between each VSV terminal and VSV body. If continuity exists, replace VSV. If continuity does not exist, apply air pressure to VSV port "E". See Figure. Air from port "E" should flow from port "G". Apply battery voltage to VSV terminals. Air from port "E" should flow from port "F". If VSV operates as specified, go to next step. If VSV does not operate as specified, replace VSV.
  13. Check for open or short 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, replace ECM and retest.
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