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Home >> Mazda >> 2001 >> MX-5 Miata Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0401: EGR System, Insufficient Flow >> Diagnosis & Repair Procedure

Diagnosis & Repair Procedure

  1. Ensure FREEZE FRAME DATA has been recorded. Check for related service bulletins. Repair as necessary and go to next step.
  2. Turn ignition off and on. Using scan tool, check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If any other DTCs are present, go to appropriate test. If no other DTCs are present, go to next step.
  3. Check vacuum hoses for plugs, cracks or damage. Repair as necessary and go to step  8. If vacuum hoses are okay, go to next step.
  4. Start engine and allow it to reach operating temperature. Using scan tool in SIMULATION TEST mode, simulate SEGRP PID steps 0 to 18. If engine speed decreases or engine stalls, go to next step. If engine speed does not decrease or engine does not stall, replace EGR valve and go to step  8.
  5. Turn engine off. Turn ignition on. Disconnect EGR boost sensor vacuum hose. Connect vacuum pump to sensor. Using scan tool, check BARO V PID. Apply vacuum to sensor. If BARO V PID voltage decreases, go to next step. If BARO V PID does not change, replace EGR boost sensor and go to step  8.
  6. Connect vacuum gauge to EGR boost sensor vacuum hose. Start engine. Using scan tool in SIMULATION TEST mode, simulate EGRBV OFF. Vacuum should be present for 3 seconds at vacuum hose. If vacuum is not present, go to next step. If vacuum is present, replace EGR boost sensor solenoid valve and go to step  8.
  7. Turn ignition off. Remove EGR valve. Ensure EGR valve base gasket is installed correctly. Repair as necessary and go to next step. If EGR valve base gasket is installed correctly, install EGR valve and go to next step.
  8. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Perform PCM adaptive memory drive mode. See DRIVE MODES  under SELF-DIAGNOSTIC SYSTEM. Using scan tool, check RFC FLAG PID. If PID data is ON, go to next step. If PID data is OFF, repeat this step.
  9. Perform EGR monitor repair verification drive mode. See DRIVE MODES  under SELF-DIAGNOSTIC SYSTEM. Access ON BOARD SYSTEM READINESS TEST menu of GENERIC OBD II FUNCTION and check DRIVE MODE completion status. If EGR system monitor is complete, go to next step. If EGR system monitor is not complete, repeat this step.
  10. Reconnect all connectors. Using scan tool, check DIAGNOSTIC MONITORING TEST RESULTS. If TEST No. 10:41:00 is within specification, go to next step. If TEST No. 10:41:00 is out of specification, replace PCM and go to next step.
  11. Cycle ignition from off to on. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If any other DTC is present, go to appropriate test.
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