Stewal

From my own experience with a standard low mileage car and original fans(2006) the drivers side does most of the work, coming on with ac and normal idling temps as required but get the car hot enough and both come on. Try giving it a bit of a spanking then let it idle until fans cut in, it will probbly trigger one then,soon after, the second. On mine, putting the ac on at these higher temps puts both fans on straight away. At least thats how it works on mine without any issues over many years, iincluding an annual trip to the Italian/Austrian passes in summer heat. its very confusing trying to fathom out the correct behaviour online because so much of the internet info is US based, and from what I can gather, the Mishimoto replacements don't follow the original pattern, but put both fans on at high speed in all circumstances.

As far as i remember there is only one crank sensor and a camshaft sensor for each bank. Each has their own fault code so unless you are getting other codes I can't see it being anything other than the throttle body its telling you.