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Engine Mount Control System: Troubleshooting

Special Tools Required 

Vacuum pump/gauge, 0-30 in.Hg

Snap-on YA4000A or equivalent, commercially available

NOTE: Check the vacuum hoses and lines for damage and proper connections before troubleshooting.

Follow this procedure if the engine vibrates excessively when idling.

  1. Start the engine, and let it idle.
  2. Raise the engine speed from idling to 2,000 rpm.
  3. Check the MOUNT CTRL SOL in the PGM-FI DATA LIST with the Honda Diagnostic System (HDS).

    Is ON indicated at idling and OFF indicated at 2,000 rpm? 

    1. YES  - Go to step 4.
    2. NO  - Update the engine control module (ECM)/ powertrain control module (PCM) if it does not have the latest software (see HOW TO UPDATE THE ECM/PCM ), or substitute a known-good ECM/PCM (see HOW TO SUBSTITUTE THE ECM/PCM ), then recheck. If the engine mount control system works properly, and the ECM/PCM was updated, the troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM (see ECM/PCM REPLACEMENT ).
  4. Turn the ignition switch OFF.
  5. Disconnect the engine mount control solenoid valve 2P connector from the engine mount control solenoid valve.
  6. Turn the ignition switch ON (II).
  7. Measure the voltage between the engine mount control solenoid valve 2P connector terminal No. 2 and body ground.
    Fig 1: Measuring Voltage Between Engine Mount Control Solenoid Valve 2P Connector Terminal 2 And Body Ground
    G03653743Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    1. YES  - Go to step 8.
    2. NO  - Repair an open in the wire between the engine mount control solenoid valve 2P connector and No. 18 (15 A) fuse in the under-dash fuse/relay box.
  8. Start the engine, and let it idle.
  9. Measure the voltage between the engine mount control solenoid valve 2P connector terminals No. 1 and No. 2, with the engine at idle.
    Fig 2: Measuring Voltage Between Engine Mount Control Solenoid Valve 2P Connector Terminals 1 And 2
    G03653744Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    1. YES  - Go to step 10.
    2. NO  - Repair an open in the wire between ECM/PCM (B7) and the engine mount control solenoid valve 2P connector. If the wire is OK, update the ECM/ PCM if it does not have the latest software (see HOW TO UPDATE THE ECM/PCM ), or substitute a known-good ECM/ PCM (see HOW TO SUBSTITUTE THE ECM/PCM ), and recheck. If the engine mount control system works properly, and the ECM/PCM was updated, the troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM (see ECM/PCM REPLACEMENT ).
  10. Raise the engine speed above 1,000 rpm.
  11. Measure the voltage between the engine mount control solenoid valve 2P connector terminals No. 1 and No. 2.
    Fig 3: Measuring Voltage Between Engine Mount Control Solenoid Valve 2P Connector Terminals 1 And 2
    G03653745Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    1. YES  - Repair a short to body ground in the wire between ECM/PCM (B7) and the engine mount control solenoid valve. If the wire is OK, update the ECM/PCM if it does not have the latest software (see HOW TO UPDATE THE ECM/PCM ), or substitute a known-good ECM/ PCM (see HOW TO SUBSTITUTE THE ECM/PCM ), and recheck. If the engine mount control system works properly, and the ECM/PCM was updated, the troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM (see ECM/PCM REPLACEMENT ).
    2. NO  - Go to step 12.
  12. Disconnect the vacuum hose (A) that is connected to the solenoid connector from the engine mount control solenoid valve (B), and connect a vacuum pump/gauge, 0-30 in.Hg, to the hose. Apply about 20 in.Hg of vacuum, and wait for 20 seconds.
    Fig 4: Disconnecting Vacuum Hose Connected To Solenoid Connector
    G03653746Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Does the engine mount hold vacuum? 

    1. YES  - Go to step 13.
    2. NO  - Either the vacuum hose or one of the engine mounts has a vacuum leak. Repair as needed.
  13. Release the vacuum, then apply vacuum again.

    Is there a noticeable change in idle smoothness with and without vacuum applied? 

    1. YES  - Go to step 14.
    2. NO  - Replace the front engine mount and/or rear engine mount.
  14. Connect a vacuum pump/gauge, 0-30 in.Hg, to the engine mount control solenoid valve port (A) that is connected to the solenoid connector.
    Fig 5: Connecting Vacuum Pump/Gauge To Engine Mount Control Solenoid Valve Port
    G03653747Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there manifold vacuum at idle, and a decrease in manifold vacuum when you raise the engine speed above 1,000 rpm? 

    1. YES  - The system is OK.
    2. NO  - Replace the engine mount control solenoid valve.
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