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Home >> Toyota >> 1998 >> Avalon XLS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Tests W/Codes >> Self-Diagnostic Tests >> DTC P0402: Excessive Exhaust Gas RECIRCULATION (EGR) Flow Detected >> Diagnosis & Repair (Using OBD-II Scan Tool)
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Diagnosis & Repair (Using OBD-II Scan Tool)

  1. Check all EGR system vacuum hoses. Replace hoses as necessary. If vacuum hoses are okay, access ECM behind glove box. Ensure ignition is off. On models with Calif. emissions and except Calif. emissions with engine immobilizer system and/or traction control, disconnect ECM E6 connector. See Figure. Connect a jumper wire between ground and terminal No. 18 (Black/White wire) at ECM E6 connector. Go to next step. On except Calif. emission models without engine immobilizer system and/or traction control, disconnect ECM E6 connector. See Figure. Connect a jumper wire between ground and terminal No. 12 (Black/White wire) at ECM E6 connector. Go to next step.
    NOTE: For information on engine immobilizer system, see COMPUTERIZED ENGINE CONTROLS in THEORY/OPERATION article.
  2. On all models, apply air pressure to EGR Vacuum Switching Valve (VSV) port "E". VSV is located under "V" bank cover on top of engine. See Figure. With jumper wire connected, air should flow from port "F". With jumper wire disconnected, air should flow from port "G". If VSV operates as specified, go to step 5). If VSV does not operate as specified, go to next step.
  3. 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.
  4. Check VSV operation. Apply battery voltage to VSV terminals. Apply air pressure to VSV port "E". See Figure. Air should flow from port "F". Remove battery voltage from VSV terminals. Air should flow from port "G". Replace VSV as necessary. If VSV is okay, check for short in EGR VSV circuits between engine compartment fuse block and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring as necessary.
  5. Disconnect vacuum hose from EGR valve. Connect a vacuum pump to EGR valve. Start engine. Apply vacuum to EGR valve. If engine does not run rough or stall, replace EGR valve. If engine runs rough or stalls, check EGR valve position sensor. See appropriate SYSTEM/COMPONENT TESTS article. Replace as necessary. If EGR position sensor is okay, replace ECM.
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