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.

Connect the Honda Diagnostic System (HDS) to the data link connector (DLC) (see step 2 on HOW TO USE THE HDS (HONDA DIAGNOSTIC SYSTEM) ).
Turn the ignition switch to ON (II).
Make sure the HDS communicates with the vehicle and the PCM. If it doesn't communicate troubleshoot the DLC circuit (see DLC CIRCUIT TROUBLESHOOTING ).
Start the engine, and let it idle.
Raise the engine speed from idling to 2,000 rpm.
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?

YES - Go to step 7.

NO - Update the powertrain control module (PCM) if it does not have the latest software (see PCM UPDATE ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ), then recheck. If the engine mount control system works properly, and the PCM was updated, the troubleshooting is complete. If the PCM was substituted, replace the original PCM (see PCM REPLACEMENT ).
Disconnect the engine mount control solenoid valve 2P connector from the engine mount control solenoid valve.
Turn the ignition switch to ON (II).
Measure the voltage between engine mount control solenoid valve 2P connector terminal No. 2 and body ground.

Fig 1: Identifying Voltage Between Engine Mount Control Solenoid Valve 2P Connector Terminal No. 2 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES - Go to step 10.

NO - Repair open in the wire between engine mount control solenoid valve 2P connector terminal No. 2 and No. 18 (10 A) fuse in the under-dash fuse/relay box.
Measure the voltage between engine mount control solenoid valve 2P connector terminals No. 1 and No. 2, with the engine at idle.

Fig 2: Identifying Voltage Between Engine Mount Control Solenoid Valve 2P Connector Terminals No. 1 And No. 2
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES - Go to step 11.

NO - Repair open in the wire between PCM (A12) and the engine mount control solenoid valve 2P connector. If the wire is OK, update the PCM if it does not have the latest software (see PCM UPDATE ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ), and recheck. If the engine mount control system works properly, and the PCM was updated, the troubleshooting is complete. If the PCM was substituted, replace the original PCM (see PCM REPLACEMENT ).
Raise the engine speed above 1,000 rpm.
Measure the voltage between engine mount control solenoid valve 2P connector terminals No. 1 and No. 2.

Fig 3: Identifying Voltage Between Engine Mount Control Solenoid Valve 2P Connector Terminals No. 1 And No. 2
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES - Repair short to body ground in the wire between PCM (A12) and the engine mount control solenoid valve. If the wire is OK, update the PCM if it does not have the latest software (see PCM UPDATE ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ), and recheck. If the engine mount control system works properly, and the PCM was updated, the troubleshooting is complete. If the PCM was substituted, replace the original PCM (see PCM REPLACEMENT ).

NO - Go to step 13.
Disconnect the vacuum hose (A) that is closest to the solenoid connector from the engine mount control solenoid valve (B), and connect a commercially available vacuum pump/gauge, 0-30 in.Hg, to the hose. Apply about 20 in.Hg of vacuum, and wait for 20 seconds.

Fig 4: Identifying Engine Mount Control Solenoid Valve And Vacuum Hose
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Do the engine mount hold vacuum?

YES - Go to step 14.

NO - Either the vacuum hose or one of the engine mount has a vacuum leak. Repair as needed.
Release the vacuum, then apply vacuum again.
Is there a noticeable change in idle smoothness with and without vacuum applied?

YES - Go to step 15.

NO - Replace the front engine mount.
Connect a commercially available vacuum pump/ gauge, 0-30 in.Hg, to the engine mount control solenoid valve (A) that is closest to the solenoid connector.

Fig 5: Identifying Engine Mount Control Solenoid Valve
Courtesy 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?

YES - The system is OK.

NO - Replace the engine mount control solenoid valve.