2015 focus st. 30k miles. Petrol. 

Started with losing revs, like it was struggling for air, then dying. Push the start button and was just turning over and not catching. Ignition off and then restart and fires up right away. Revs to 5k then choking and dying. This was the previous Saturday. 

A week later I started it no problem. Brilliant! Went a run and it drove superb. Pulled up and switched it off. Went to start it and coughing again. 

Plugged obd in and was saying fuel system fault. Bought a new fuel system control module (5336501) as read these can go. 

fitted this on the following Thursday and put the ignition on and got the red engine fault and no start. Plugged in the obd and it won't communicate. Getting the red light on the obd connector so it's giving power. 

swapped back to the old fuel module in case the new one was the fault but still the same. Borrowed my pals top notch obd computer, reads the vin but won't communicate further. Was reading 11v on the screen so bought a new battery. Car hasn't had much use lately and had some cold weather so could be the fault. Nope. Still no obd communication and still red engine management symbol. 

after trying to communicate with the obd the ignition restarts itself so there's some communication but not reading properly. 

went from running rough out the blue to not starting at all. New batteries in the key fobs and placed in the arm rest. 

also throwing up low brake fluid fault (checked and fine) and tyre pressure fault (also fine). 

ready for burning the thing!! 

please help! 

Also... I'd read about the washer pump causing water to run along the wiring. Checked the fuses and plugs under the passenger footwell (mine is rhd) and everything looks corrosion free, clean and dry. 

Hi Jon, I commend your enthusiasm but slow down and don't keep throwing money at the problem. First you need to be able to read the fault codes, the best way is to buy a modifyed ELM327 lead, for example eBay:  https://www.ebay.co.uk/itm/ELM327-USB-modified-for-ELMconfig-HS-CAN-MS-CAN-Forscan-ELMcon-npH-wk/373408935554?hash=item56f0e82e82:g:gUkAAOSwysFcAOo-

Next get a laptop and download ForScan (its Free) read how to use it or ask for help on here. ForScan will give a list of problems and a good indication as to where to start fault finding.

The washer pump water problem probably does not effect your car, but if you want to check it then you need to disconnect the plug to the BCM and check the connector and pins for signs of corrosion.

Thanks for the reply. 

I used my forscan at first that diagnosed the fuel pump issue. Then when the part arrived and was fitted the dash showed the red engine fault. Plugged forscan in but wouldn't communicate. Got the first green symbol but they wouldn't talk. Plugged in my bluefin and got E001 error. But when the error code comes up it restarts the ignition so something it communicating. 

Borrowed a MaxiCOM off a pal. It reads the vin but can't communicate further. So it connects slightly but not enough to diagnose. 

 

I don't then know if the faults are related or a crazy coincidence. It was reading no problem. I'd taken the remap off thinking it was causing the rough running on the Saturday and it limped onto the driveway with just the rev issue. Next time I tried to start it was the Thursday when the part arrived and it displayed the red engine management fault. Very odd

Opened up the housing for the ECU and it's fried. Water has got in. 

 

Well you found it 🙂. Now you just have to find how the water got there. peel back the insulation tape on the harness and check to see if there is any water.

Maybe your car is affected by the screen wash pump fault but that goes to the BCM and not the ECU, so I think probably not.

One thing is for sure you need to find the water, if its done it once it will do it again, and congratulations on at least finding the fault, good luck