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Home >> Toyota >> 1996 >> T100 Base, 2D Pickup, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Tests W/Codes - 3.4L >> Circuit Tests >> DTC P0402 - Excessive Exhaust Gas RECIRCULATION (EGR) Flow Detected (2WD Models) >> 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. Sensor is located at right rear of engine. Read 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 E6 connector. See Figure and 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. Inspect EGR VSV. Using scan tester, select ACTIVE TEST mode. Check operation of VSV when activated by scan tester. See appropriate illustration in THEORY/OPERATION - 3.4L article for VSV location. Start and run engine. With EGR system in OFF mode, air from port "E" should exhaust from small filter on end of valve. See Figure. With EGR system in ON mode, air from port "E" should exhaust from port "G". If valve operates correctly, check EGR valve. See SYSTEM/COMPONENT TESTS article. If VSV does not operate correctly, go to next step.
  5. Turn ignition off. Remove EGR VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 33-39 ohms at 68°F (20°C). Measure resistance between each terminal and body of valve. Resistance should be infinite. If resistance is not as specified, replace VSV. If resistance is as specified, go to next step.
  6. Check EGR VSV operation. Apply battery voltage to VSV terminals. Air from port "E" should exhaust from small filter on end of valve. See Figure. Remove battery voltage from valve terminals. Air from port "E" should exhaust from port "G". Replace VSV as necessary. If VSV operates as specified, go to next step.
  7. Check for a short circuit in wiring harness between EGR VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest.
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