Originally posted by th10000
The ECO light is only on when the VCM is in 3 cylinder mode.
How do you know that you are not running on 6 cylinders when the ECO light is on? Until I had this vibration issue, there was no way to know for sure whether it was on 6 or 3 cylinders. That is why there has been discussion on this board about what exactly the ECO ligth represented.
When it switches to 6 it feels a bit like a downshift, but you can see there is no change to the tachometer speed. Even if it were just the torque converter unlocking, there would be a change in tach.
There is a distinct power difference between 3 and 6 cylinder mode. I can only accelerate under certain conditions in 3 mode. The limit is easily reached on flat terrain, if you try anything but very gentle acceleration. But push too hard, you can hear and feel the switchover -- again, almost like a downshift, a somewhat subtle downshift, but it isn't a downshift. It is much easier to keep it in 3 cylinder mode at 60-65 MPH than it is at 70-75 MPH.
You can also shut the ANC off using the radio easter egg (turn radio off. Then while holding 1+6 together press "on". Then release all 3 buttons. Then press 1 to turn ANC on/off. You have to hit 1 a couple of times to get around a test mode, detailed in a TSB posted somewhere else on the site). With ANC off, you can more easily hear when the engine is in what mode. I did this for a couple of weeks until I was convinced that the light coordinated with the mode.
A side note, I was also surprised how well the ANC worked. It really was most effective at slower speeds, between 45-60MPH, ESPECIALLY with the engine under load, like going up a slight grade, you can really hear the 3 cylinder "hum". Above 65 it seemed perhaps that ANC was needed less.