Driving on the highway at 75 mph when this message pops up, along with the check engine light. Pulled over to the shoulder and turned car off. After 10 mins got back on the highway. Car was running fine although check engine light remained on. Pulled into Advanced Auto Parts store and the diagnostic said something to the affect of a "solenoid in or near the transmission" (Not exactly sure what I was told) Anyhow brought it to the transmission shop in town here. The shop is going to change the transmission fluid this week however he had no logical explanation for what had happened. I am going to ask a few more mechanics this week but I'm afraid most of these people are clueless when it comes to the Chevy Volt. I have 60,000 miles on the car. Drove it from San Diego to Chicago no problem straight gasoline. It has since been on the highway 9 or 10 times however no more than 250 mile round trips. I regularly charge the car every night at home. It has always been a great ride/car. This has me baffled and I'm appreciative of any and all feedback here. Thank you.