This is a curiosity thing mostly, and frankly not something I am going to look into as I hate auto start / stop. But my newly aquired used truck, does not auto stop when coming to a red light (like all the trucks next to me). When I bought it, the starter was replaced 300 miles prior with a new ford unit. In the PCM there was a trouble code for "Starter Performance" , and RR tail lamp short or open circuit. I fixed the bad bulb and cleared the codes. After all emmissions monitors completed there are no hidden codes yet it does not auto stop. Any ideas?