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Home >> Toyota >> 1996 >> 4Runner Base, 4WD, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Tests W/Codes - 2.7L >> Circuit Tests >> DTC P0402 - Excessive Exhaust Gas RECIRCULATION (EGR) Flow Detected >> Diagnosis & Repair (Using Toyota Scan Tester)
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Diagnosis & Repair (Using Toyota Scan Tester)

  1. Connect scan tester. See Figure. Turn ignition on. Read EGR gas temperature. If temperature is 302°F (150°C), go to step 4). If temperature is not 302°F (150°C), go to next step. If temperature displayed is 318.7°F (159.3°C), there is a short in EGR temperature sensor circuit.
  2. Disconnect EGR temperature sensor connector. Monitor EGR gas temperature. If EGR gas temperature is not 37.6°F (3.1°C), go to next step. If temperature is 37.6°F (3.1°C), replace sensor and retest.
  3. Turn ignition off. Access ECM behind glove box. Disconnect ECM E7 connector. See Figure. Turn ignition on. Using scan tester, read EGR gas temperature. If EGR gas temperature is 37.6°F (3.1°C), inspect and repair open in circuits between ECM and EGR temperature sensor. If temperature is not 37.6°F (3.1°C), replace ECM and retest.
  4. Using scan tester, select ACTIVE TEST mode. Check operation of VSV when activated by scan tester. VSV is located near intake plenum.
  5. Start and run engine. With EGR system off, air from port "E" should exhaust from port "F". See Figure. With EGR system on, air from port "E" should not exhaust from port "F". If valve operates correctly, check EGR valve. See SYSTEM/COMPONENT TESTS article. If valve does not operate correctly, go to next step.
  6. 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.
  7. Check VSV operation. Apply battery voltage to VSV terminals. Air from port "E" should exhaust from port "F". See Figure. Remove battery voltage from valve terminals. Air from port "E" should not exhaust from port "F". Replace VSV as necessary. If VSV operates as specified, go to next step.
  8. Check for an open circuit in wiring harness between engine compartment fuse block and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
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