According to the logic table in the schematic, the only difference between resitance and capacitance is that FC4 is high (DGND) for resistance and forced low (V-) for capacitance. Since FC4 is normally high (DGND) via an internal pullup resistor, something is pulling it to V-.
This leaves two options:
1. Diode D4 is shorted to V- via FC1. If this is the case, removing this diode should force it into resistance mode (the capacitance selection would not work) as long as the internal pull-up resistor is undamaged.
2. The internal pull-up resistor is damaged. If after removing D4, the meter still insists on capacitance mode this is the most likely cause. A 2.5MOhm resistor between the FC4 pin (Pin 119) and DGND (Pins 3-5 or left leg of the voltage regulator) would mimic the internal pullup in the ES51922.
3. The internal circuitry for FC4 is damaged, the meter is toast.