Hi, I am new to this forum. Thought to join it as we have had a ford focus for years and the latest one we had just gives us trouble all the time. It is a Ford Zetec1.6. Since we bought it loads of repairs have been done. Just last year the throttle body has been replaced. Lately the yellow engine light keeps coming on. Initially no fault codes could be identified so the garage cleared them. Just a week later it came up again and it was diagnosed as ignition coil. we had it replaced and a day later the yellow engine light came on again. Had it diagnosed again and no codes came up. So cleared it and a day later on again. It seems to drive fine but I think I read too much into it. It is low on power, at least it feels like it as our previous car had a bigger engine. But it always had been low on power. We disconnected the battery but light stays on. We are now not sure whether or not to invest further into this car to get this fault fixed as some seem to think it could be the ECU and that is expensive or just count our losses and move on to another car. Any advice on similar experiences would be much appreciated.

what year is the car? 

 

I would recommend buying a modified ELM cable and download forscan and do your own comprehensive diagnostic test. Its more likely to pull an error than generic tools.