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Home >> Lexus >> 1998 >> ES 300 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Tests >> DTC P0402: Excessive 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 and retest system. If vacuum hoses are okay, access ECM behind glove box. Ensure ignition is off. Disconnect ECM E7 harness connector. Turn ignition on. Connect a fused jumper wire between ground and terminal No. 18 (Yellow/Green wire) at ECM E7 connector.
  2. Apply compressed air to EGR VSV port "E". See Figure. With fused jumper wire connected to ground, air should flow from port "F". With fused jumper wire disconnected, air should flow from port "G". If EGR VSV operates as specified, go to step 6). If EGR VSV does not operate as specified, go to next step.
  3. Remove EGR VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 27-33 ohms at 68°F (20°C). Measure resistance between each terminal and body of valve. Resistance should be infinite. If resistance is as specified, go to next step. If resistance is not as specified, replace EGR VSV.
  4. Apply compressed air to port "E" of EGR VSV. Air should flow from port "G". Using fused jumper wires, apply battery voltage and ground to EGR VSV terminals. Again, apply compressed air to port "E". Air should flow from port "F". Replace EGR VSV as necessary.
  5. If valve meets all specifications, check for an open in wiring harness and connectors between engine compartment junction block and ECM E7 connector. See appropriate wiring diagram in SYSTEM WIRING DIAGRAMS article. Repair as necessary.
  6. Disconnect vacuum hose from EGR valve. Start engine. Apply vacuum to EGR valve. If engine runs rough or stalls, go to next step. If engine does not stall or run rough, check EGR valve intake and exhaust passages. If passages are clean, replace EGR valve and retest system.
  7. Check EGR Vacuum Control Valve (VCV). See SYSTEM/COMPONENT TESTS article. Replace VCV as necessary. If VCV is okay, replace ECM and retest system.
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