Siemens Washing Machine I-DOS not working.

I have been called to a Siemens WM14YH8TGB washing machine.
The automatic I-DOS dispenser is not dispensing either the detergent or fabric conditioner. Both items stopped working at the same time.
The customer has kept the dispenser very clean. There is continuity to both sensors and pumps in the dispenser drawer lid.
I found one of the contacts in the back of the drawer gummed up with a bit of detergent. I have cleaned the contacts and tightened the connectors to the PCB.
These are very difficult to test as there is very little space in the back of the connectors for access with a probe.
What voltage do the dosing pumps work at? Will the dosing system work if the machine registers there’s no detergent/fabric conditioner in the dispenser?
Is there a likely component that would cause this fault?
Any advice on this would be appreciated.