A diagnostic method for a weighing scale having multiple force measuring devices , comprising: selecting a plurality of like weighing scale components to be monitored; selecting as a diagnostic parameter an operating parameter that is common to the selected like weighing scale components and should have approximately the same value for each component during normal operation; receiving at a computer device from each of the selected weighing scale components , an output signal representative of the selected diagnostic parameter; at the computer device , calculating a deviation of the output signal value received from each selected weighing scale component with a stored value established during a known good state of weighing scale component operation; characterized in that at the computer device , calculating a total deviation by summing the calculated output signal value deviations of each selected weighing scale component ; at the computer device , comparing the calculated total deviation against a first predetermined threshold value; wherein if the total deviation is determined by the computer device to exceed the first predetermined threshold value, using the computer device to calculate the percentage of total deviation that is attributable to each selected weighing scale component ; subsequently at the computer device , comparing the percentage of total deviation that is attributable to each selected weighing scale component to a second predetermined threshold value; and wherein if the percentage of total deviation attributable to a given selected weighing scale component is determined by the computer device to exceed the second predetermined threshold value, using the computer device to indicate a problem. selecting a plurality of like weighing scale components to be monitored; selecting as a diagnostic parameter an operating parameter that is common to the selected like weighing scale components and should have approximately the same value for each component during normal operation; receiving at a computer device from each of the selected weighing scale components , an output signal representative of the selected diagnostic parameter; at the computer device , calculating a deviation of the output signal value received from each selected weighing scale component with a stored value established during a known good state of weighing scale component operation; characterized in that at the computer device , calculating a total deviation by summing the calculated output signal value deviations of each selected weighing scale component ; at the computer device , comparing the calculated total deviation against a first predetermined threshold value; wherein if the total deviation is determined by the computer device to exceed the first predetermined threshold value, using the computer device to calculate the percentage of total deviation that is attributable to each selected weighing scale component ; subsequently at the computer device , comparing the percentage of total deviation that is attributable to each selected weighing scale component to a second predetermined threshold value; and wherein if the percentage of total deviation attributable to a given selected weighing scale component is determined by the computer device to exceed the second predetermined threshold value, using the computer device to indicate a problem. <EOS>