Engine Management Light & Service Light Comes on When Turning Heating on!

So my Citroen Picasso C3 (2014) has an intermittent issue. When you put the air blowers on the service light flashes up and the display reads "Engine Fault Repair Needed". The service light used to flash up intermittently every now and on various drives but it did switch itself off. However now, its now happening all the time, as soon as I put the heaters on. By the way the car has been serviced by Citroen this year and I have a good few months left.

What's actually happening now is the engine management light is permanently on, so as soon as I start the car up the message "Engine Fault Repair Needed" is on and will not go off. If I put the heaters on the service light still comes on after 5 seconds or so and will turn itself off if I turn them off, but not the engine management light is staying on.

I took it to a local garage who diagnosed the fault as the "Throttle Body". He cleaned it out as it had a lot of carbon in it, and must have reset the engine management light, and It was good for about two days - however I didn't touch the heaters over these two days and now, today, as I put them on the same thing happens, and I'm back to square one with the permanent engine management light on and warning message. I called them to find out if it could be anything else they could check but they said the code only read "ThrottleBody". Which they cleaned out.

I suspect there could be a faulty sensor that is causing this to happen, or some kind of short. But I'm stuck as what to do? I am going to buy my own diagnostic tool either way. My options seem that I keep throwing money at local garages who will go round in circles grabbing at straws, or take it direct to Citroen, who will charge a fortune.

ANY help would be massively appreciated.
Thank you.
Steve

DigitalEmotion76 wrote: ↑Fri Dec 14, 2018 4:08 pm I am going to buy my own diagnostic tool either way

Hi DigitalEmotion76, I would definitely agree with getting your own code reader, something like this KW808 would be ok for reading engine codes.

If you need to get into the other ECUs on the car, you will need access to lexia. But this is a bit more complicated to set-up.

DigitalEmotion76 wrote: ↑Fri Dec 14, 2018 4:08 pm I took it to a local garage who diagnosed the fault as the "Throttle Body". He cleaned it out as it had a lot of carbon in it,

There is no throttle body on the diesel engines. I think you have not been given the correct information.