Solution
Yes, when you fix the impedance range, it affects the accuracy of the measurement for capacitor. You need to choose right impedance range for your measurement. In the PXIe-4190 Specification, you can find following part.
The figure shows capacitor impedance magnitude versus test frequency to help quickly identify the appropriate impedance range for your measurements. From your measurement frequency and capacitor you can choose approximate impedance range. When you choose auto range, it would be done automatically.