Id say theres a fault in the BCM (Body Control Module), its the computer module that controls all the systems you mentioned including the low speed cooling fan.If the BCM is replaced with a second hand unit,you will need the exact same type and level of BCM, there are different level BCM's depending on the car and the option level,eg-whether is a calais or executive etc. You will also need the ignition key fob from the same car the BCM comes from,otherwise the immobiliser wont turn off, as your key's security code will be different to the new BCM security code,and these codes have to match..You just gotta swap over the second hand keyfob with your keyfob,it unscrews from the actual metal part of the ignition key.You will also need to get the BCM linked to the ECU (Electronic Control Unit),you will have to see holden about this,it needs to be done with the Tech2 scantool.