Torque converter lockup not engaging?

[scoot]

Greetings! I have a 2003 Vibe (regular model with automatic transmission) with about 103K on it, and lately I've noticed that the torque converter does not seem to be locking up during highway driving. Whenever I'm on the highway the RPM will not drop a few hundred after I stop accelerating when it's in high gear, which from what I understand means that it is not locking up. My gas mileage is a few MPG lower than it has been in recent months, but that could very well be due to the cold weather.Has anyone had an issue like this with their Vibe? And what are some possible causes of this problem? One possibility I read is that there is a solenoid that controls the torque converter lockup, which can fail. However the article (http://forums.genvibe.com/zerothread?id=34859) said that the condition triggered a check engine light....my Vibe has never had the check engine light go off! Although these don't seem likely, could it have something to do with the cold weather or possibly the ECU? Or is it likely that the torque converter unit as a whole needs to be replaced?Any advice would be greatly appreciated. thanks!

[Lysander]

Do you know that your check engine light works? Does it come on briefly when you turn the key to 'run' prior to starting the engine?

[THE VIBERATOR]

I agree with Lysander...check to make sure your check engine light works when you turn the car to the "on" position (not starting the car). It should come on for about 3 seconds or so then go away if there's no problem.