I recently purchased a used 2011 Lexus RX450h and have noticed that the eco light does not turn on when I am driving, even though the eco mode is on. What is the difference between the eco light and the eco mode? And does my eco light not working, just mean that the indicator light is burnt out or that my hybrid traction battery is not working? Any help would be greatly appreciated. Thank you.

 

eco mode is an active feature, you act to turn it on using the steering wheel buttons
and the car acts differently. Major users of power such as the HVAC, cruise and throttle
all use less, softer throttle performance, diminished A/C output and relaxed cruise response.
See page 174 in the owner's manual

The ECO light is a passive feature, when you drive light footed it rewards you with a simple
green light...does not change the car, it is trying it change you! See page 160 in OM.

My dad installed a vacuum gauge in our 383 Dodge Polara to try for better MPG's.
Funny how the gauge bottomed out whenever the glorious Wide Open Throttle sucking
sound filled the cabin when I drove it!

 

Additionally, the ECO light specifically just comes on when the needle is in one of the first two ECO ranges (the two before the "Power" range). Its not very useful, it really only duplicates info from the power gauge anyway. I believe it is a dealer option to turn it off completely, so if yours does not come on at all (assuming it does when all the lights come up at startup for bulb check), then it may have been disabled by the dealer from previous owner.

Other than sharing the first 3 letters, the two "ECO" lights have nothing to do with each other, and is not any kind of error indication.

 

As mentioned, "ECO Mode" is a green-on-black icon that tells you the car is in a mode where, for instance, the heater blower motor is not as forceful, and the accelerator pedal is much less aggressive. The "ECO Driving Light" is a black-on-green icon that just tells you that you are being easy on the gas. This latter icon bugged the heck out of me when I first bought the car, but it's something you can turn off. Check your manual, I forget how to do it.