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Diagnosis & Repair (Using Toyota Scan Tool)

  1. Connect scan tool. See Figure. Start and run engine. Allow engine to reach normal operating temperature. Using scan tool, read EGR gas temperature. If temperature is 50-302°F (10-150°C), go to step 5). If temperature is not 50-302°F (10-150°C), go to next step.
    NOTE: If EGR gas temperature reading is 37.6°F (3.1°C), an open exists in EGR temperature sensor circuit. If temperature reading is 318.7°F (159.3°C), a short exists in EGR temperature sensor circuit.
  2. Disconnect EGR temperature sensor connector. Sensor is mounted on manifold between EGR valve and air intake chamber. Connect a jumper wire between EGR temperature sensor connector terminals. Turn ignition on. If EGR temperature displayed is not 318.7°F (159.3°C), remove jumper wire and go to next step. If temperature displayed is 318.7°F (159.3°C), remove jumper wire. Recheck EGR temperature. If EGR temperature displayed is not 37.6°F (3.1°C), go to step 4). If temperature displayed is 37.6°F (3.1°C), check temperature sensor connector terminals. Repair as necessary. If connector is okay, replace sensor.
  3. Turn ignition off. Access ECM behind glove box. On models with Calif. emissions and except Calif. emissions with engine immobilizer system and/or traction control, connect a jumper wire between terminals No. 13 (Green/Yellow wire) and No. 18 (Brown wire) at ECM E7 connector. See Figure. On except Calif. emission models without engine immobilizer system and/or traction control, connect a jumper wire between terminal No. 14 (Green/Yellow wire) at ECM E6 connector and terminal No. 22 (Brown wire) at ECM E7 connector. See Figure. On all models, turn ignition on. If EGR temperature displayed i s not 318.7°F (159.3°C), check ECM connectors. Repair as necessary. If connectors are okay, replace ECM. If temperature displayed is 318.7°F (159.3°C), locate and repair open in wiring harness between ECM and EGR temperature sensor.
    NOTE: For information on engine immobilizer system, see COMPUTERIZED ENGINE CONTROLS in THEORY/OPERATION article.
  4. Remove jumper wire. On models with Calif. emissions and except Calif. emissions with engine immobilizer system and/or traction control, disconnect ECM E7 connector. See Figure. On except Calif. emission models without engine immobilizer system and/or traction control, disconnect ECM E6 connector. See Figure. On all models, recheck EGR temperature. If EGR temperature displayed is not 37.6°F (3.1°C), check ECM connectors and repair as necessary. If connectors are okay, replace ECM. If temperature displayed is 37.6°F (3.1°C), locate and repair short in wiring harness between ECM and EGR temperature sensor.
  5. Check all EGR system vacuum hoses. See appropriate illustration in VACUUM DIAGRAMS article. Repair vacuum hoses as necessary. If all hoses are okay, check EGR VSV. Using scan tool, select ACTIVE TEST mode. Check operation of VSV when activated by scan tool. VSV is located under "V" bank cover on top of engine.
  6. Start and run engine. With EGR system off, air from port "E" should flow from port "G". See Fig 1. With EGR system on, air from port "E". should flow from port "F". If valve operates as specified, go to step 8). If valve does not operate as specified, go to next step.
  7. Remove EGR VSV. Using ohmmeter, measure resistance between VSV terminals. Resistance should be 27-33 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". Air should flow from port "F". Remove battery voltage from valve terminals. Air should flow from port "G". Replace VSV as necessary. If VSV is okay, check for open in EGR VSV circuits between engine compartment fuse block and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
  9. Perform EXHAUST GAS RECIRCULATION (EGR) SYSTEM TEST. See EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM/COMPONENT TESTS article. Replace components as necessary. If EGR system is functioning properly, check EGR Vacuum Control Valve (VCV). See appropriate SYSTEM/COMPONENT TESTS article. Replace as necessary. If VCV is okay, replace ECM.
Fig 1: Identifying EGR VSV & Vapor Pressure Sensor VSV
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