So I had an '06 M35X and drove it 100K miles, then upgraded to a '15 Q70 Sport AWD. With both of these vehicles, I never had a "major" repair, except for maybe control arms on all cars.

This week I was driving on the highway and the check engine light illuminates, then I noticed the water temp was pinned in the red color! WOW! So I slowed down and pulled over and shut off the car. Whew. I waited a bit, I restarted the car, and it idled okay, but when I started to accelerate over 1200rpm +/- it lunged and jerked before and would not shift into second gear. This was bad.

I remembered that I purchased one of those OBD wireless devices on Amazon. An app called ODD Fusion can read the engine codes, provide some actual data stored in the computer, and even shows "gauges." Cool! So the engine temp was in fact 240 deg or higher. The trigger code was P1712.

AAA towed me on a flatbed to the local dealer. Then I had to take an Uber home (and back to the dealership later) since they had no loaner vehicles. The Uber driver even made a comment that the dealerships have been calling Ubers for their customers to get home, but not mine. Hmmm.

The dealer said they didn't know if the transmission or drivetrain failed, etc. My car has 69K miles and the service advisor said I'm lucky since the drivetrain was under warranty through 70K miles. That was last night. This morning they called and said it was only the thermostat that failed So they replaced that and flushed and replaced the coolant in the radiator all as warranty service and I had my beloved Q70 S back. Whew!

I think I've had that little OBD plug-in module with wireless in my center console for a few years and only used it once when it arrived. I was happy I had that and the app on my phone to get some quick info.

Glad it was something simple! The jerking and bucking was possibly the car going into limp mode to protect itself.

I have an ODBII reader as well and it is always connected. I periodically will check my cars vitals while driving just to keep an eye on it.