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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 OBD-II Scan Tool)
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Diagnosis & Repair (Using OBD-II Scan Tool)

  1. Disconnect EGR temperature sensor. EGR temperature sensor is mounted on EGR valve body on top right rear of engine. Using ohmmeter, measure resistance between EGR temperature sensor terminals (not immediately after driving vehicle). If resistance is 2500 ohms or more, go to next step. If resistance is less than 2500 ohms, replace EGR temperature sensor.
  2. Check for short circuit in wiring harness between EGR temperature sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring as necessary. If wiring harness is okay, go to next step.
  3. Access ECM behind passenger's side kick panel. Ensure ignition is off. Disconnect ECM E5 connector. Turn ignition on. Connect a jumper wire between ground and terminal No. 12 (Red/White wire) at ECM E5 connector.
  4. With jumper wire connected, EGR Vacuum Switching Valve (VSV) is on. Apply air pressure to EGR VSV port "E". See Figure. Air from port "E" should flow through filter on end of EGR VSV. Disconnect jumper wire. Air from port "E" should flow from port "G". If EGR VSV operates as specified, check EGR valve. See appropriate SYSTEM/COMPONENT TESTS article. Replace EGR valve as necessary. If EGR VSV does not operate correctly, go to next step.
  5. Turn ignition off. Remove EGR VSV. Using ohmmeter, measure resistance between VSV 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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