Freelander 1 Help with park sensor problem needed

Hi Guys, well first of all let me apologise for not been here in a while, various reasons pc died lost everything and had to save up for new one and have been concentrating on my new business too.

The latest issue I have tried to tackle is my rear park sensors on my 2006 Td4 facelift. I bought a set of 4 as the middle two on my vehicle were NOT ticking so I planned on removing the bumper and doing them this weekend, however Yesterday on here I read the post about drilling them out instead ( Thanks great advice ).
I drilled out the two offending ones and it worked a treat so plugged in the new ones and hey presto they were ticking. I thought that would make everything work but it's no different no sound and orange flashing park sensor switch.
I have put my volt meter in the two wires that seem to feed a small speaker bolted onto the rear of what I think is the ECU for the sensors and have 12v (see pics), is this speaker seperate and would it still illuminate the orange light if it is faulty or do I have a knackered ECU.
At some point a towbar is fitted to the wires as shown and I wondered if something had been left off so sensors dont work when towing and there is a white connector not doing anything, I'm not great on electrics and could do with some guidance please, what's Your thoughts please ! Cheers Al.

Ps. Think my voltmeter was connected wrong way round shows - 12 v lol

Well Guys great success with the sensors they are fixed. Recap of symptoms no ticking on middle two sensors, no sound, orange/red flashing switch light.
After following tip on here two sensors drilled out and replaced ticking sound now evident on all 4, but still flashing switch light and no sound.
I didn't know if the speaker was inoperative whether it could keep the flashing switch symptom or not hence my request on here if anyone knew!
I decided to take a chance and found a speaker for a discovery and it was just the internal bit not the plastic housing, I checked the part number and found it was same for freelanders so at £18 I took a chance and ordered it off E bay.
Tonight I loosened the drivers side rear boot panel and behind the park sensor ECU bolted to the back is the speaker held on with 2 x 7 mm nuts.
I removed the speaker just clipped in and fitted a new one and tested the park sensors and hey presto solid light on switch and sound, just one more reason to love my Freelander TD4 even more lol. Photos attached hope this helps someone else, AL.