LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Isuzu >> 1996 >> Trooper SE >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P0401 - EGR Flow Insufficient
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P0401 - EGR Flow Insufficient

  1. Perform On-Board Diagnostic (OBD) System Check. Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
  2. If DTC P1406 is also set, go to DTC P1406. If DTC P1406 is not set, go to next step.
  3. Inspect exhaust system for modifications or leaks. If a problem is found, repair as necessary and go to step 6). If no problem is found, go to next step.
  4. Remove EGR valve and check pintle, valve and passages and adapter for excessive deposits or restriction. Check EGR valve gasket and pipes for leaks. If a problem is found, repair as necessary and go to step 6). If no problem is found, go to next step.
  5. Remove EGR inlet and outlet pipes from exhaust and intake manifolds. Inspect manifold EGR ports and pipes for blockage. If a problem is found, repair as necessary and go to next step. If no problem is found, check for an intermittent problem. See TESTS W/O CODES article.
  6. Read and record FAIL RECORDS data for DTC P0401. Clear DTCs. Start engine and monitor system info screen while moving connectors and wiring harnesses related to EGR valve. If scan tool displays DTC P0401 FAILED THIS TEST, go to last step completed in this DTC test. If scan tool does not display DTC P0401 FAILED THIS TEST, check for an intermittent problem. See TESTS W/O CODES article.
scientia non olet · About LEMON Manuals