There are a number of reasons for the power train light to come on and the vehicle go into limp home mode with Ranger/BT50 models. Trans temp, the split turbo pipe as mentioned but a drop in battery voltage to the point that the auto trans computer will not function will also cause it to go into limp home mode. Don't ask how I know. There is also a software upgrade on some models. My mates Ranger went into limp home mode West of the Isa last year. I got it going as I have a scan tool and cancelled the error codes which read it was a turbo boost controller sensor error. Every 200ks or so it would do it again. We got it through to Darwin and it was due to a software error that Ford knew about and had an upgrade for. After the upgrade no more issues. His model is a bit later than mine and my model doesn't have the issue. What got me is that Ford didn't automatically do the upgrade unless you had a problem. Great when you are 200ks west of Isa with nothing about for miles.