Engine Mount Control System Symptom Troubleshooting - Engine vibrates excessively when idling
Engine vibrates excessively when idling
Special Tools Required
Vacuum Pump/Gauge, 0?30 inHg Snap-on YA4000A or equivalent, commercially available
NOTE:
Check the vacuum hoses and the lines for damage and proper connections before troubleshooting.
Check the liquid filled engine mount for damage. The rubber mount should have dimples in it. This is normal. If the internal bladder ruptures, the rubber mount looks like it is bulging. If the engine mount is damaged, replace it.
1.
MOUNT CTRL SOL signal check:

MOUNT CTRL SOL signal check
?1.
Connect the HDS to the DLC.

?2.
Press the engine start/stop button to select the ON mode.

?3.
Make sure the HDS communicates with the vehicle and the PCM. If it does not communicate, troubleshoot the DLC circuit.

?4.
Check for DTCs. If a DTC is present, diagnose, and repair the cause before continuing with this test.


?5.
Start the engine, and let it idle.

?6.
Check the parameter(s) below with the HDS.
Signal
Current conditions
Values
Unit
MOUNT CTRL SOL
    

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

     
YES
     
     
     
Go to step 2.
     
NO
     
     
     
Update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If the PCM was substituted, and the symptom/indication goes away, replace the original PCM.?
2.
Open wire check (IG1 (VBSOL) line):

Open wire check (IG1 (VBSOL) line)
?1.
Press the engine start/stop button to select the OFF mode.

?2.
Disconnect the following connector.
Engine mount control solenoid valve 2P connector

?3.
Press the engine start/stop button to select the ON mode.

?4.
Measure the voltage between test points 1 and 2.
Test condition
ON mode
 
Engine mount control solenoid valve 2P connector: disconnected
Test circuit
IG1 (VBSOL)
Test point 1
Engine mount control solenoid valve 2P connector No. 2 (TAN)
Test point 2
Body ground


Is there battery voltage?

     
YES
     
     
     
Go to step 3.
     
NO
     
     
     
Repair an open in the IG1 (VBSOL) wire between the engine mount control solenoid valve 2P connector terminal No. 2 and the under-dash fuse/relay box.?
3.
Open wire check (MCS line):

Open wire check (MCS line)
?1.
Start the engine, and let it idle.

?2.
Measure the voltage between test points 1 and 2.
Test condition
Engine running
 
Engine mount control solenoid valve 2P connector: disconnected
Test circuit
MCS
Test point 1
Engine mount control solenoid valve 2P connector No. 2 (TAN)
Test point 2
Engine mount control solenoid valve 2P connector No. 1 (GRN)


Is there battery voltage?

     
YES
     
     
     
Go to step 4.
     
NO
     
     
     
Repair an open in the wire between PCM connector terminal C14 and engine mount control solenoid valve 2P connector terminal No. 1.
If the wire is OK, update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If the PCM was substituted, and the symptom/indication goes away, replace the original PCM.?
4.
Shorted wire check (MCS line):

Shorted wire check (MCS line)
?1.
Raise the engine speed above 2,000 rpm.

?2.
Measure the voltage between test points 1 and 2.
Test condition
Engine speed above 2,000 rpm
 
Engine mount control solenoid valve 2P connector: disconnected
Test circuit
MCS
Test point 1
Engine mount control solenoid valve 2P connector No. 2 (TAN)
Test point 2
Engine mount control solenoid valve 2P connector No. 1 (GRN)


Is there battery voltage?

     
YES
     
     
     
Repair a short to ground in the wire between PCM connector terminal C14 and engine mount control solenoid valve 2P connector terminal No. 1.
If the wire is OK, update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If the PCM was substituted, and the symptom/indication goes away, replace the original PCM.?
     
NO
     
     
     
Go to step 5.
5.
Engine mount check 1:

Engine mount check 1
?1.
Press the engine start/stop button to select the OFF mode.

?2.
Disconnect the upper vacuum hose (A) from the engine mount control solenoid valve (B), and connect a vacuum pump/gauge, 0?30 inHg, to the hose.


?3.
Apply about 20 inHg of vacuum, and wait 20 seconds.

Does the engine mount hold vacuum?

     
YES
     
     
     
Go to step 6.
     
NO
     
     
     
Either the vacuum hose or the front engine mount has a vacuum leak.?
6.
Engine mount check 2:

Engine mount check 2
?1.
Start the engine, and let it idle.

?2.
Release the vacuum, then apply vacuum again.

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

     
YES
     
     
     
Go to step 7.
     
NO
     
     
     
7.
Engine mount control solenoid valve check:

Engine mount control solenoid valve check
?1.
Connect a vacuum pump/gauge, 0?30 inHg, to the vacuum hose (A).


Is there manifold vacuum at idle, and a decrease in manifold vacuum when you raise the engine speed above 2,000 rpm?

     
YES
     
     
     
The system is OK.?
     
NO