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fan controller is part of main car ecu,, by default some fault codes will trigger the fan to switch on to protect it self,, more like its a reactive thing rather than the fault,,, but the fault code will trigger it,
need to scan car with a P-code scanner ie scans dealer only codes as these will trigger fan coming on..
if going to a garage and they have snap on diagnostics would need the European update on it or wont scan mini correctly,,
fact the fan runs shows the fan works so no would not replace that it works, fan only picks up power from the relay in under bonnet fusebox,, this relay is controlled by 12v feed from main ecu,, movtronic part of ecu is where its switched from,, ie where everything is brought together 5v rail and can bus system and bin files that are stored codes etc,, car when switched on the ecu goes in to self check for any issues if finds them flag EML and in some cases throws the fan on from cold,, common things like cat issues or 02 sensor or temp sensor issues will cause this,, ie a broken temp sensor or wrong type sensor will be seen by the ecu as car over heating as even on a sensor that is open circuit the ecu sees this as high temp and throws fan on etc. not saying its not the ecu but most times its something outside causing it, and without scan gear and good knowledge of the system its near impossible ,, find a auto electrician best way forward,,
 

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Discussion Starter #22
Thought I should post an update here.

Brought the Mini to a BMW mechanic. They did their thing and came back with the following:

  • the guys that did the timing chain/head rebuild must have got the wiring connectors mixed around for the temp sensor (and something else - can’t remember), so naturally I did the same when replacing the thermostat housing. That was apparently causing the camshaft sensor to trigger the noticeable rough idle.
  • there was a wonky intermittent oil pressure Issue with the VANOS.
In hindsight, I did a lot more than I probably should have, but eh, it gave me something to do being unemployed during a pandemic.

I really appreciate your input on everything! Your last post made me admit defeat. Haha
 

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Thought I should post an update here.

Brought the Mini to a BMW mechanic. They did their thing and came back with the following:

  • the guys that did the timing chain/head rebuild must have got the wiring connectors mixed around for the temp sensor (and something else - can’t remember), so naturally I did the same when replacing the thermostat housing. That was apparently causing the camshaft sensor to trigger the noticeable rough idle.
  • there was a wonky intermittent oil pressure Issue with the VANOS.
In hindsight, I did a lot more than I probably should have, but eh, it gave me something to do being unemployed during a pandemic.

I really appreciate your input on everything! Your last post made me admit defeat. Haha
your totally welcome ,, they really can be so whats the best word for it hmmmm and problem child more times than not, i'm surprised it never fried the temp sensor if put 12v thermostat plug to it ,, but that would makes sense as 12v would of pushed the ecu to over its 5v rail voltage and register 168c temp all the time which would on first start ups tri[p the ecu in to closed loop running then the ecu would see the readings off the 02 sensors and have fit as nothing would add up and it would keep switching in and out of loop etc,, really a hard car to diagnose at times and without some diagnostics tools and can be a fair bit of time as well,, i get it all the time i say to someone need to book it in and i will work through they then ask how long and what sort of costs ,,, hmmmm electronic faults are the worst sometimes i find it within 10 minutes and some have been a day on it picking it off,,
 
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