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DTC P0401: EGR Flow Too Low: Testing

NOTE: Record freeze frame data has been recorded. Check for service bulletins and on-line information.
  1. Turn ignition off, then on. If no other DTCs are present, go to next step. If any other DTCs are present, repair other DTCs first.
  2. Check all vacuum hoses for clogging, damage or leaks. If problems are not present, go to next step. If any problems are present, repair as necessary and go to step  7 .
  3. Start engine and warm up to operating temperature. Using scan tool, select SEGRP PID. Operate EGR at 0 to 18 steps. If engine speed drops or engine stalls, go to next step. If RPM does not change, replace EGR valve and go to step  7 .
  4. Turn ignition off. Turn ignition on. Using scan tool, select BARO V PID. Disconnect EGR boost sensor vacuum hose. Using a vacuum pump, apply vacuum to EGR boost sensor. If BARO V PID decreases, go to next step. If BARO V PID does not decrease, replace EGR boost sensor and go to step  7 .
  5. Start engine. Disconnect vacuum hose to EGR boost sensor. Using scan tool, select EGRBV off simulation. If manifold vacuum is not felt at vacuum hose and go to next step. If manifold vacuum is felt at vacuum hose, replace EGR boost solenoid valve. Go to step  7 .
  6. Turn ignition off. Remove EGR valve. If gasket is okay, go to next step. If gasket installation is faulty, repair as necessary and go to next step.
  7. Reconnect all components. Turn ignition on. Using scan tool, clear DTC. Start engine. Conduct Drive Mode No. 1 under DRIVE CYCLE PROCEDURE. See DRIVE MODES  under SELF-DIAGNOSTIC SYSTEM. Check RFC FLAG PID. If RFC FLAG PID is on, go to next step. If RFC FLAG PID is not on, repeat Drive Mode No. 1.
  8. Conduct Drive Mode No. 2 under DRIVE CYCLE PROCEDURE. See DRIVE MODES  under SELF-DIAGNOSTIC SYSTEM. Using scan tool on-board system readiness test function, check EGR system monitor completion status. If system has been monitored, go to next step. If system has not been monitored, repeat Drive Mode No. 2.
  9. Reconnect all components. Using scan tool diagnostic monitoring test results function, check TEST ID 10:41:00. If value is okay, go to next step. If value is not okay, replace PCM. PCM is mounted to passenger floor, behind glove box. Go to next step.
  10. Perform after repair procedure. See AFTER REPAIR PROCEDURE  . If DTC is not present, testing is complete. If any DTC is present, go to appropriate test for diagnosis and repair.
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