I am confused about your caravan, In your previous thread about water being lost through the non return valve, you posted pictures of the plumbing close to the Truma water heater. On the wall there is what appears to be an external pump connection with a purple and white wire connected.
In the wiring diagram Toad A Caravan has posted for both the 2001 and 2003 GTS's there is only an internal water pump shown. This suggests a previous owner may have reworked the system to use an external pump.
On the assumption the modification to to use an external pump simply used the original pump wiring, then +ve 12V dc should be supplied from fuse board (ESM-2000) on the Purple and Black wire to the microswitches in each tap. The output) from the micro switches should be "on" when the tap is open and "off" when the taps are closed. that should feed into the Purple and Yellow wire which goes into the the Pump master switch (KT9-GT)
The output from the pump master switch is on the Purple and Orange wire which should go to the water pump +ve terminal on the external wall connector. All th e 0V wires seem to be White and Orange.
The symptoms you are describing suggest the 12V fuse for the pump in the ESM-2000 may have blown, Or a wire has come loose somewhere. This would prevent 12V from reaching the pumps connection terminals.
If the fuse has blown, the question is why, You need to be aware the submersible pumps rely on the movement of cold water through them to keep them at normal operating temperatures. If for any reason such as the pump running dry or if the water flow has been stopped but the pump keeps running (Fault micro switch or a tap has not been fully turned off properly) the pump can overheat and destroy itself. Being out side it may not be heard.