circulation is set at some predetermined value by the manufacturer of the automatic transmission the cooling system of a land motor vehicle along with all above mentioned components is well known the cooling system is required to maintain the engine at an operating temperature and to prevent breakdown of the engine due to overheating referring to fig2 the motor vehicle 40 is presented having a front wheel drive the conduit 33 is attached to the heat exchange unit 28 and the internal combustion engine 27 the atf circulates through the conduit 33 in directions 34 and 35 as shown in fig2 the in line sensor 45 is inserted into the conduit 33 and is connected with the microprocessor 50 and the readout means 52 the microprocessor 50 receives data from the characteristic fluid sensor means a b and c as explained above in connection with fig3 which are inserted as a part of the in line sensor 45 the readout means 52 may be digital or analog moreover the readout means 52 may be located on the dashboard of the motor vehicle 40 or be a separate diagnostic tool used in repair and or maintenance the digital read out is preferred for the purposes of repair and or maintenance the data shows the health and or status of the automatic transmission system of the motor.