August 19, 2013, 12:54 pm
given the nature of your symptoms, it sounds a lot like you will have an electrical fault, possibly combined with a sensor fault.
You say that this issue always occurs after a dewy night? in which case it sounds like there is moisture getting somewhere it shouldnt be. My first bet would be to pop the bonnet, and check the auxhillary fuse box, make sure there is no sign of moisture on the fuses or relays, hopefully it should be bone dry and thoroughly sealed. Secondly I would check the internal fusebox, it could be that the moisture has been transferred inside and has gathered on the main fuseboard. So start with these and ensure both are safe and dry.
Secondly you should check the OBD port, make sure that its not shorted out in any way and doesnt have an adapter in it, as the bluetooth communicating can cause similar problems, but I dont believe that this will directly be your issue.
If the above are all clear, then you are probably looking at a loom issue, I would start by disconnecting the battery and then going to the fuseboard under the passenger footwell. Remove and reseat the wiring harnass.
Secondly go under the bonnet, and just check all the connections, make sure there is no evidence of heat / fluid damage around the wiring. You may also find it beneficial to remove the headlights for this, so that you can see more of the underside and see more of what is going on.
Next job is to see if you can reforce the issue. Take your car to a hand wash where they use pressure washers, and give the eastern europeans a tenner to give your car a good going over. The pressure will test the seals and will allow moisture in where it shouldnt be, in the event that there is water ingress and the error occurs, you need to check all the above again to make sure that you dont have any obvious water damage. You may find that this is a moisture going through the pollen filter and off to the fuseboard. A very discreet problem, that can cause a good deal of chaos.
Let me know how you get on!