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DTC P1491 -'01 Model: EGR Valve Insufficient Lift

  1. Reset the PCM (see HOW TO RESET THE PCM )
  2. Start the engine Hold the engine at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on.
  3. Test-drive the vehicle under load for about 10 minutes Try to keep the engine speed in the 1,700-2,500 rpm range
  4. Check for a Temporary DTC with the scan tool or the HDS

    Is Temporary DTC P1491 indicated? 

    1. YES:  Go to step 5.
    2. NO:  Intermittent failure, system is OK at this time Check for poor connections or loose terminals at the EGR valve and at the PCM.
  5. Turn the ignition switch OFF.
  6. Disconnect the EGR valve 6P connector.
  7. Start the engine, and let it idle.
  8. Measure voltage between EGR valve 6P connector terminals No 4 and No 6.
    Fig 1: Measuring Voltage Between EGR Valve 6P Connector Terminals No. 4 & No. 6
    G01511798Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    1. YES:  Substitute a known-good PCM, and recheck (see HOW TO SUBSTITUTE THE PCM FOR TESTING PURPOSE ) If the symptom/indication goes away, replace the original PCM.
    2. NO:  Go to step 9.
  9. Turn the ignition switch OFF.
  10. Turn the ignition switch ON (II).
  11. Measure voltage between EGR valve 6P connector terminals No 2 and No 3.
    Fig 2: Measuring Voltage Between EGR Valve 6P Connector Terminals No. 2 & No. 3
    G01511799Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there about 5 V? 

    1. YES:  Go to step  13.
    2. NO:  Go to step 12.
  12. Measure voltage between PCM connector terminals A28 and A30.
    Fig 3: Measuring Voltage Between PCM Connector Terminals A28 & A30
    G01511800Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there about 5 V? 

    1. YES:  Repair open in the wire between the EGR valve and the PCM (A28, A30).
    2. NO:  Substitute a known-good PCM and recheck (see HOW TO SUBSTITUTE THE PCM FOR TESTING PURPOSE ). If the symptom/indication goes away, replace the original PCM.
  13. Turn the ignition switch OFF.
  14. At the sensor side, measure resistance between EGR valve 6P connector terminals No. 1 and No. 2.
    Fig 4: Measuring Resistance Between EGR Valve 6P Connector Terminals No. 1 & No. 2
    G01511801Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity or resistance of 100 kΩ or more? 

    1. YES:  Replace the EGR valve.
    2. NO:  Go to step 15.
  15. Measure resistance between EGR valve 6P connector terminals No. 1 and No. 3.
    Fig 5: Measuring Resistance Between EGR Valve 6P Connector Terminals No. 1 & No. 3
    G01511802Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there 100 k ohms or more? 

    1. YES:  Replace the EGR valve.
    2. NO:  Go to step 16.
  16. Reconnect the EGR valve connector.
  17. Turn the ignition switch ON (II).
  18. Measure voltage between PCM connector terminals A16 and A28.
    Fig 6: Measuring Voltage Between PCM Connector Terminals A16 & A28
    G01511803Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there about 1 2V? 

    1. YES:  Go to step  21.
    2. NO:  Go to step 19.
  19. Turn the ignition switch OFF.
  20. Check for continuity between PCM connector terminal A16 and body ground.
    Fig 7: Checking For Continuity Between PCM Connector Terminal A16 & Body Ground
    G01511804Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES:  Repair short in the wire between the EGR valve and PCM (A16).
    2. NO:  Repair open in the wire between the EGR valve and PCM (A16).
  21. Turn the ignition switch OFF.
  22. Disconnect the EGR valve 6P connector.
  23. Connect the battery positive terminal to EGR valve 6P connector terminal No. 4 with a jumper wire.
    Fig 8: Connecting The Battery Positive Terminal To EGR Valve 6P Connector Terminal No. 4 With A Jumper Wire
    G01511805Courtesy of AMERICAN HONDA MOTOR CO., INC.
  24. Start the engine, and let it idle. Then connect the battery negative terminal to EGR valve 6P connector terminal No. 6 with a jumper wire.

    Does the engine stall or run rough? 

    1. YES:  Go to step 25.
    2. NO:  Replace the EGR valve.
  25. Turn the ignition switch OFF.
  26. Disconnect PCM connector B (24P).
  27. Check for continuity between PCM connector terminal B3 and body ground.
    Fig 9: Checking For Continuity Between PCM Connector Terminal B3 & Body Ground
    G01511806Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES:  Repair short in the wire between the EGR valve and the PCM (B3).
    2. NO:  Go to step 28.
  28. Connect EGR valve 6P connector terminal No. 4 to body ground with a jumper wire.
    Fig 10: Connecting EGR Valve 6P Connector Terminal No. 4 To Body Ground With A Jumper Wire
    G01511807Courtesy of AMERICAN HONDA MOTOR CO., INC.
  29. Check for continuity between PCM connector terminal B3 and body ground.
    Fig 11: Checking For Continuity Between PCM Connector Terminal B3 & Body Ground
    G01511808Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES:  Go to step 30.
    2. NO:  Repair open in the wire between the EGR valve and the PCM (B3).
  30. Disconnect the jumper wire from the EGR valve 6P connector.
  31. Check for continuity between EGR valve 6P connector terminal No. 6 and body ground.
    Fig 12: Checking For Continuity Between EGR Valve 6P Connector Terminal No. 6 & Body Ground
    G01511809Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES:  Substitute a known-good PCM and recheck (see HOW TO SUBSTITUTE THE PCM FOR TESTING PURPOSE ). If the symptom/indication goes away, replace the original PCM.
    2. NO:  Repair open in the wire between the EGR valve and G101.
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