Originally Posted by velocity

as far as i know there is a tie up between the act and cts sensor(the blue watertemp one).if one or the other fails, depending on which one is faulty the ecu subtitutes fixed values on the failed one depending on the readings from the good one,and if both fail then it still substitutes a set value for both, i dont know if only applies to standard ecu's
but it might be worth changing the cts sensor just to see if thats the one with the problem as opposed to the act one.