LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Toyota >> 2000 >> RAV4 Base, AWD, Standard >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Control System Self-Diagnostics >> Diagnostic Tests >> DTC P0401: Insufficient Exhaust Gas RECIRCULATION (EGR) Flow Detected >> Diagnosis & Repair (Using Toyota Hand-Held Tester)
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnosis & Repair (Using Toyota Hand-Held Tester)

  1. Check vacuum hoses. See VACUUM DIAGRAMS article. If problem exists, repair vacuum hoses as necessary. If problem does not exist, go to next step.
  2. Connect hand-held tester to Data Link Connector (DLC) No. 3. See Figure. Disconnect EGR VSV vacuum hoses. Select ACTIVE TEST mode on hand-held tester. Check operation of EGR VSV when activated by scan tool. With EGR system off, air applied to port "E" should flow from small filter on end of EGR VSV. See Fig 1. With EGR system on, air applied to port "E" should flow from port "G". If EGR VSV operates as specified, go to step  5. If EGR VSV does not operate as specified, go to next step.
  3. Disconnect EGR VSV harness connector. Measure resistance between EGR VSV terminals (component side). Resistance should be 33-39 ohms at 68°F (20°C). Check for continuity between each terminal and body of EGR VSV. Continuity should not exist. If readings are as specified, go to next step. If readings are not as specified, replace EGR VSV.
  4. Apply battery voltage and ground to EGR VSV terminals. Apply air pressure to port "E". Air should flow from small filter on end of EGR VSV. See Fig 1. Remove battery voltage from EGR VSV terminals. Air should flow from port "G". If problem exists, replace EGR VSV. If problem does not exist, repair open or short in wiring between engine compartment fuse block and ECM. See WIRING DIAGRAMS article.
  5. Perform exhaust gas recirculation system test. See EXHAUST GAS RECIRCULATION (EGR) SYSTEM TEST under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, repair as necessary. If problem does not exist, go to next step.
  6. Check EGR vacuum modulator. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, replace EGR vacuum modulator. If problem does not exist, go to next step.
  7. Check EGR valve. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, replace EGR valve. If problem does not exist, go to next step.
  8. Check Manifold Absolute Pressure (MAP) sensor. See ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, replace MAP sensor. If problem does not exist, replace ECM.
Fig 1: Identifying EGR Vacuum Switching Valve (VSV) Ports
G95F31380Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
scientia non olet · About LEMON Manuals