Facelift rear parking sensor fault

[megatron-uk]

Since I bought my 2017 GT, the rear parking sensors have shown a fault - I've tried two sets of parking sensors (loom + sensors + number plate bulbs, complete), and the head unit still shows it as faulty. VCDS shows no power to any of the sensors, and therefore no calibration data/readings from any of them.

I stripped out the boot today to try and get a look at the rear control unit/sounder.... but I found that on a facelift car there is NO rear control unit - the wiring from the rear bumper disappears straight up behind the right hand trim and over the wheel arch. Although the bracketry is still there as on older cars there is nothing fitted to it, and the loom is has no join in it, so it's not as if a previous owner has stripped it out and rejoined the wiring.

Does anyone have any idea of how the rear parking sensors are controlled/powered in facelift cars?

[megatron-uk]

Facelift rear loom

IMG_20230902_162240_(1080_x_1440_pixel).jpg

[megatron-uk]

The other single wire is for my reversing camera, btw - so nothing to do with the parking sensors.

Output from VCDS when scanning the park assist module:

Code: Select all

------------------------------------------------------------------------------
Address 10: Park/Steer Assist (J446)       Labels:| 5Q0-919-294.clb
   Part No SW: 1K8 919 472 C    HW: 5Q0 919 294 A
   Component: PARKHILFE 8K  H03 0480  
   Revision: --------    Serial number: 39331720804555 Dataset Number: 0001
   Coding: 0031051001
   Shop #: WSC 00020 999 00000
   ASAM Dataset: EV_EPHVA18VW364GP00 001007
   ROD: EV_EPHVA18VW364GP00_VW32.rod
   VCID: 3753E5108ECEEF2B32-8063

1 Fault Found:
1080083 - Rear Parking Aid Sensor(s) 
          B107B 13 [009] - Open Circuit
          Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 3
                    Fault Frequency: 1
                    Reset counter: 166
                    Mileage: 62731 km
                    Date: 2023.06.10
                    Time: 05:07:26

[megatron-uk]

Headunit error:

IMG20230902172723.jpg

[Marius336]

the module is behinde the cover on the front windshild wiper. Open the Cover, then look at plugs, maybe water from Sunnroof ore use the plug to test for continuity.

the rear sensors are on the big plug.

[megatron-uk]

Thanks. No sunroof fitted, but the location of the module is a big help, thank you.

[megatron-uk]

I confirmed that voltage was getting to the rear sensors via the loom and, not having any easy way of testing the sensors (short of pulling the front bumper off and plugging each on in turn, since the front works perfectly) I decided to replace them all and buy a new rear loom as well.

I didn't want to pull the rear bumper off just to test, so I unclipped the bumper harness underneath and plugged the replacement loom and new sensors in; just on the floor. It all worked perfectly; head unit display showed the reversing sensor bar lines and putting my hand over each sensor in turn showed them all working.

So, either a (or several) breaks in the 'original replacement' rear harness I bought, or possible faulty used sensors. Either way, I now have a fully working set of front and rear parking sensors. Just need to give these new ones a quick spray to match the body (they were standard black coloured), and then try to find a time when I can take the rear bumper off to remove the faulty parts and swap this harness over.