mk 4 golf lambda sensor heater fault

hi, i have a vw golf 1.6, bcb engine.
i have had it scanned and got the following fault codes

17834 - tank ventilation valve open circuit

17524 - o2 sensor heater circuit, bank 1 sensor1 open

17526 - o2 sensor heater circuit, bank 1 sensor2 open


i have replaced both the pre and post cat lambda sensors but these fault codes still come back even after they have been cleared.

i used ngk sensors so i am wondering if i need to get genuine vw sensors or could there be anything else that would cause a fault, both connectors seemed to be very clean..

also, what do i need to do about the tank valve, i am reluctant to change/but new parts if the faults are connected and i do not need one.

any more info needed please ask.

thanks

check fuse 43

i have just checked fuse 43 and sure enough it was blown..
one new fuse and i have been able to clear all codes, taken car for a spin and all seems fine, thank you very much for the info, saved me some money for now..

without a wiring diagram, i presume that both systems are linked to fuse 43 but what would be the reason for the fuse to blow..?
what would be the chances of it blowing again..?