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Home >> Toyota >> 1998 >> T100 DX, 4WD, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Tests W/Codes - V6 >> Self-Diagnostic Tests >> DTC P0402: Excessive Exhaust Gas RECIRCULATION (EGR) Flow Detected (2WD 1/2 Ton Models With Regular Cab) >> Diagnosis & Repair (Using Toyota Scan Tool)
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Diagnosis & Repair (Using Toyota Scan Tool)

  1. Connect scan tool. See Figure. Turn ignition on. Using scan tool, read EGR gas temperature (not immediately after driving vehicle). If EGR gas temperature is 302°F (150°C), go to step 4). If EGR gas temperature is not 302°F (150°C), go to next step.
    NOTE: If EGR gas temperature displayed 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 EGR valve body on top 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 EGR gas temperature is 37.6°F (3.1°C), replace sensor.
  3. Turn ignition off. Access ECM behind passenger's side kick panel. Disconnect ECM E5 connector. See Figure. Turn ignition on. Using scan tool, read EGR gas temperature. If EGR gas temperature is 37.6°F (3.1°C), locate and repair open circuit in wiring harness between ECM and EGR temperature sensor. If EGR gas temperature is not 37.6°F (3.1°C), replace ECM.
  4. Check EGR VSV. Using scan tool, select ACTIVE TEST mode. EGR VSV is located on top left rear of engine. Check operation of EGR VSV when activated by scan tool. Apply air pressure to EGR VSV port "E". See Figure. With EGR system in OFF mode, air from port "E" should flow from small filter on end of EGR VSV. With EGR system in ON mode, air from port "E" should flow from port "G". If EGR VSV operates as specified, check EGR valve. See appropriate SYSTEM/COMPONENT TESTS article. If EGR VSV does not operate as specified, 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 VSV terminal and body of EGR VSV. Resistance should be infinite. If resistance is not as specified, replace EGR VSV. If resistance is as specified, go to next step.
  6. Check EGR VSV operation. Apply battery voltage to EGR VSV terminals. Apply air pressure to EGR VSV port "E". See Figure. Air from port "E" should flow from small filter on end of EGR VSV. Remove battery voltage from EGR VSV terminals. Air from port "E" should flow from port "G". Replace EGR VSV as necessary. If EGR VSV operates as specified, go to next step.
  7. Check for short circuit in wiring harness between EGR VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring as necessary. If wiring harness is okay, replace ECM.
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