Hi please help me. 

I  own a low mileage 43k toyota yaris (EU)

It had always been reliable. No problems. one day it started to have erratic starting. Would crank but not start when the engine was warm (for example had driven to a store to get milk, it drove there, but wouldnt start to return home). Eventually once the car had cooled down, it started again. 

It began cutting out when driving. Which was dangerous and scary. It was towed to toyota maindealer as it wasnt showing any fault code, the engine management light was not on either. 

Toyota said it was ECU and replaced it. I picked up the car, it did same thing straight away. I replaced the battery. It did the same and was taken again to toyota. Within 2 weeks of picking the car up and it stalliing in their garage forecourt. Toyota did not want responsibility. Eventually they said they had tested it, it had cut out 7 times. 

But they wanted me to collect the vehicle without doing any work. 

The car was left there for months. As I had another car to drive and it was stressing me out. When I couldnt drive the other car anymore. I called if they could give the car MOT and pay for a full service. It hadnt been serviced for a while and I thought that might help. It was ok the first day, the second day it had  trouble starting. Again trouble starting when the engine was warm. 

I put wynns extreme petrol system cleaning in, it was slightly improved. But it still had problems starting when warm. But not always. Sometimes it started again straight away. 

I then bought an obd2 scanner. It said that it was cam position sensor p0340 fault code. I was relieved, I called toyota and to their credit they agreed to put one in for free. 

I was full of hope this morning. I went to garage, handed over the car, they gave me back the car with old cam position sensor in a box. I drove the car a few miles, then stopped. I tried to start again. It was cranking. Opened the bonnet, engine was hot... - i had been driving. 

I plugged in the 0bd2 scanner, to see if the fault returned after clearing the code. No fault came up this time. 

Symptoms of the car, are very similar to cam position sensor, rough idle, (depsite toyota has just serviced) erratic engjine power, problems pulling off, erratic starting when engine warm. Fortunately it hasnt yet cut out when driving. But it was high revs and only going 57mph in 5th gear. 

Does anyone have any idea? 

Thank you