Diagnosis & Repair (Using Toyota Scan Tool)

Check EGR system vacuum hoses. See appropriate illustration in VACUUM DIAGRAMS article. Replace vacuum hoses as necessary. If all hoses are okay, go to next step.
Using scan tool, select ACTIVE TEST mode. Check operation of VSV when activated by scan tool. VSV is located under front of intake manifold. Start and run engine. With EGR system off, air from VSV port "E" should flow from small filter on end of valve. See Fig 1. With EGR system on, air from port "E" should flow from port "G". If valve operates as specified, go to step 6). If valve does not operate as specified, go to next step.
Remove EGR VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 33-39 ohms at 68°F (20°C). Check for continuity between each terminal and body of valve. If continuity exists, replace VSV. If continuity does not exist, go to next step.
Check VSV operation. Apply battery voltage to VSV terminals. Apply air pressure to VSV port "E". Air from port "E" should flow from small filter on end of valve. See Fig 1. Remove battery voltage from valve terminals. Air from port "E" should flow from port "G". Replace VSV as necessary. If VSV operates as specified, go to next step.
Check for open or short circuit in wiring harness between instrument panel fuse block and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring as necessary.
Check EGR system and components. See appropriate SYSTEM/COMPONENT TESTS article. Replace as necessary. If EGR system is okay, check Manifold Absolute Pressure (MAP) sensor. See appropriate SYSTEM/COMPONENT TESTS article. Replace MAP sensor as necessary. If MAP sensor is okay, replace ECM.

Fig 1: Identifying EGR Vacuum Switching Valve (VSV)