So this connector is coming from the loom of wires of the 3 connectors that connect to the PDC.
Does anyone know what this is for?
https://i.ibb.co/JF8NS6C/20210522-232613.jpg

There's no sound coming from any of the sensors.
PDC light will come on in reverse and start blinking, but nothing is going on.

https://i.ibb.co/93h6T9g/20210523-000415.jpg https://i.ibb.co/fFJmHhK/20210523-000514.jpg https://i.ibb.co/jg2FZnD/20210523-000532.jpg https://i.ibb.co/zGLJtwS/20210523-001543.jpg https://i.ibb.co/c1Vn4r9/20210523-000717.jpg https://i.ibb.co/mJh3MXP/20210523-000543.jpg https://i.ibb.co/j4vbTFY/20210523-000539.jpg

I wonder if I should just replace the module and see what happens

Looks like X362 - rear PDC speaker (gong) connector....

Yes both pdc speakers were disconnected, hence the errors.
I connected the front speaker, and the front error went away.
https://i.postimg.cc/n9pRz4yN/20210523-134026.jpg

Next I disconnected the blue connector from the module, which is responsible for the front sensors.
I got the error that 4 front sensors were faulty and one rear.
I was kinda confused why a rear sensor is showing an error when only front ones are disconnected.

So having pressed the PDC button, the rear sensors started making the clicking sound, except the one which showed errors.
So I swapped the sensors around and turned our the one rear sensor was back.
So I borrowed one sensor from the front and installed it in the back. Now all sensors in the back were clicking and the error about rear sensor went away.

https://i.postimg.cc/JGtgBqDW/20210523-134330.jpg

https://i.postimg.cc/0rVFQ3Nf/20210523-134346.jpg

Now I tried disconnecting the white connector on the right of the module.
In this case, it gives me error that all rear and front connectors are faulty and none of then click.
https://i.postimg.cc/XBZMKSN9/20210523-134134.jpg

https://i.postimg.cc/gxVCHKpt/20210523-134205.jpg

I guess I now know for a fact that all the rear sensors are good but front ones seems to be harder to diagnose.

I checked voltage on rear connectors. One wire out of three has 12 volts.

Then I checked voltage on 2 front connectors, which are accessible without removing the bumper. They don't have voltage.
Then I checked connector X300 (the middle connector on the PDC unit). Pins 1, 4 and 9 have voltage.

Did some more poking around.

Tested pins on the PDC itself where connectors X18013 and X18362 connect.

https://i.ibb.co/WvyZBxg/Screenshot-...127-Chrome.jpg https://i.ibb.co/ky3v40Q/Screenshot-...042-Chrome.jpg https://i.ibb.co/q5XHj98/Screenshot-...551-Chrome.jpg

Pins 4, 5, and 12 all have 12 volts. Which tells me that the PDC outputs voltage to both front and rear sensors.

However I measure 0 volts on the front sensor connectors.

Now there's definitely some short in the wiring.

If I'm measuring voltage on the white (right) terminal I have 12 volts on pins 4, 5, 6 and 12.
Now if I plug in the blue connector ( X18362 ) into the PDC, I lose voltage on the white connector terminal right away.

So basically the PDC stops outputting voltage to the rear sensors as soon as I connect the connector for front sensors (X18362).

This tells me where's some kind of short it the wiring that goes to the blue connector.

Disconnected the connectors and started checking for resistance.
So on the blue connector for the front sensors, I found a short between pins 4 and 7, I.e. resistance is 0
Pin 4: Positive activation, front center right converter
Pin 7: Ground, front center right converter

So I guess the short could be at the connector of the center right sensor? That requires bumper removal :(
I wonder if the parking sensor itself could've shorted out or the problem is in the wiring?