LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Honda >> 2004 >> Civic Si >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Variable Valve Timing Electronic Control System (VTEC) And Variable Valve Timing (VTC ) System (Hatchback) >> DTC Troubleshooting >> DTC P0340: CMP Sensor A No Signal, DTC P0344: CMP Sensor A Intermittent Interruption
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P0340: CMP Sensor A No Signal, DTC P0344: CMP Sensor A Intermittent Interruption

  1. Reset the ECM (see HOW TO UPDATE THE ECM ).
  2. Start the engine.

    Is DTC P0340 and/or P0344 indicated? 

    YES:  Go to step 3.

    NO:  Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at CMP sensor A and at the ECM.

  3. Turn the ignition switch OFF.
  4. Disconnect the CMP sensor A 3P connector.
  5. Turn the ignition switch ON (II).
  6. Measure voltage between CMP sensor A 3P connector terminal No. 3 and body ground.
    Fig 1: Measuring Voltage Between CMP Sensor A 3P Connector Terminal No. 3 And Body Ground
    G01399485Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    YES:  Go to step 7.

    NO:  Check the No. 4 ACG (10A) fuse in the under-dash fuse/relay box. If the fuse is OK, repair open in the wire between CMP sensor A, and No. 4 ACG (10A) fuse.

  7. Measure voltage between CMP sensor A 3P connector terminal No. 1 and body ground.
    Fig 2: Measuring Voltage Between CMP Sensor A 3P Connector Terminal No. 1 And Body Ground
    G01399486Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there about 5 V? 

    YES:  Go to step 8.

    NO:  Go to step  10.

  8. Measure voltage between CMP sensor A 3P connector terminals No. 2 and No. 3.
    Fig 3: Measuring Voltage Between CMP Sensor A 3P Connector Terminals No. 2 And No. 3
    G01399487Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    YES:  Go to step 9.

    NO:  Repair open in the wire between CMP sensor A and G101.

  9. Substitute a known-good CMP sensor A and recheck.

    Is DTC P0340 and/or P0344 indicated? 

    YES:  Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck (see ECM UPDATING AND SUBSTITUTION FOR TESTING ). If the symptom/indication goes away with a known-good ECM, replace the original ECM.

    NO:  Replace the original CMP sensor A (see CMP SENSOR A REPLACEMENT ).

  10. Measure voltage between ECM connector terminal A25 and body ground.
    Fig 4: Measuring Voltage Between ECM Connector Terminal A25 And Body Ground
    G01399488Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there about 5 V? 

    YES:  Repair open in the wire between the ECM (A25) and CMP sensor A.

    NO:  Go to step 11.

  11. Turn the ignition switch OFF.
  12. Disconnect ECM connector A (31P).
  13. Check for continuity between ECM connector terminal A25 and body ground.
    Fig 5: Checking For Continuity Between ECM Connector Terminal A25 And Body Ground
    G01399489Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES:  Repair short in the wire between the ECM (A25) and CMP sensor A.

    NO:  Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck (see ECM UPDATING AND SUBSTITUTION FOR TESTING ). If the symptom/indication goes away with a known-good ECM, replace the original ECM.