Podmods, Maintenance, Tips and Tricks : Intermittent "Check Engine" light when towing

The light has only come on while towing, and only when restarting the truck after a stop for lunch, gas, etc.

After 3 different mechanic visits and two paid repairs (a new thermostat and a new fuel pump contoller) failed to fix the problem, I finally shelled out $70 for a little Bluetooth dingus that sits in the diagnostic port and lets me do my own code reads on my iPhone. That makes me feel a little better about ignoring the Check Engine light, since at least I can see if it's that same strange "temp sensor erratic" code and not something new. (At least for now that's a cheaper "buy my way out" solution than getting a new TV!)