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Home >> Toyota >> 1997 >> Camry LE, 2.2 G >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Tests W/Codes - 2.2L >> Circuit Tests >> DTC P0401: Insufficient Exhaust Gas RECIRCULATION (EGR) Flow Detected >> Diagnosis & Repair (Using Toyota Scan Tool)
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Diagnosis & Repair (Using Toyota Scan Tool)

  1. Check vacuum hoses. See appropriate illustration in VACUUM DIAGRAMS - 2.2L article. Repair vacuum hoses as necessary. If all hoses are okay, check VSV. Using scan tool, select ACTIVE TEST mode. Check operation of VSV when activated by scan tool. VSV is located under air intake chamber assembly.
  2. Start and run engine. With EGR system off, air should flow from small filter on end of VSV. See Fig 1. With EGR system on, air should flow from port "G". If VSV operates as specified, go to step  6). If VSV does not operate as specified, go to next step.
  3. Remove EGR VSV. Using ohmmeter, measure resistance between VSV terminals. Resistance should be 33-39 ohms at 68°F (20°C). Check for continuity between each terminal and body of VSV. If continuity exists, replace VSV. If continuity does not exist, go to next step.
  4. Check VSV operation. Apply battery voltage to VSV terminals. Apply air pressure to port "E". Air should flow from small filter on end of VSV. See Fig 1. Remove battery voltage from VSV terminals. Air should flow from port "G". Replace VSV as necessary. If VSV operates as specified, go to next step.
  5. Check for open or short circuit in wiring harness between engine compartment fuse block and ECM. See appropriate wiring diagram in WIRING DIAGRAMS - 2.2L article. Repair wiring as necessary.
  6. Check EGR vacuum modulator. See SYSTEM/COMPONENT TESTS - 2.2L article. Replace EGR vacuum modulator as necessary. If EGR vacuum modulator is okay, check EGR valve. See SYSTEM/COMPONENT TESTS - 2.2L article. Replace EGR valve as necessary. If components are okay, go to next step.
  7. Check Manifold Absolute Pressure (MAP) sensor. See SYSTEM/COMPONENT TESTS - 2.2L article. Replace MAP sensor as necessary. If MAP sensor is okay, replace ECM and retest.
Fig 1: Identifying EGR Vacuum Switching Valve (VSV)
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