Parking distance sensor problem

**k_rider** · 13-10-2014, 10:18 PM

I've recently started having problems with one of the front parking distance control sensors on my vRS (MY11) after driving in the rain. It would seem that water is getting into one of the sensors, causing the system to think an object is being detected at minimum distance (so continuous tone and red graphic on the screen).

Has anyone else experienced the same thing and resolved it? Anyone know the structure of the sensors themselves or how the system is designed, ie, is each of the four sensors on the bumper a combined transmitter and receiver (this would be my guess), or are there two transmitters/two receivers. I do have a reasonable working knowledge of ultrasonic transducers and range finding.

I'm thinking that water is somehow getting trapped in the sensor and effectively blocking it, causing an immediate 'echo' in the sensor, hence the minimum distance warning. Maybe there's some other gunk in there that needs to be cleaned out? FWIW, I've often wondered about the vulnerability of the PDC sensors to water/road grime/dust/insects.

**vdubmotorworx** · 14-10-2014, 05:29 AM

The sensors are a sealed unit. If you use VCDS you can see what the sensors are reading in MM and see which one is incorrect and replace that one by removing the bumper. If you dont have access to VCDS then you might be able to work out which one via your screen display... usually its just a replace item unless water at the connector itself....VDUB...

**wai** · 14-10-2014, 05:58 AM

The sensors multiplex, so they are each a transmitter and receiver (although not at the same time).

Do you get a graphic display indicating which sensor is triggering?

**Antiplastix** · 14-10-2014, 07:00 AM

My Mk.2 did it all the time. Didn't really worry me. Just get out and thump the offending sensor, to dislodge the water.

**k_rider** · 14-10-2014, 11:28 PM

Thanks guys for your replies.

I have access to VCDS, however accessibility is usually inversely proportional to the occurrence of the problem! I'll try dousing the suspect sensor with a hose and check out VCDS. Although when I washed the car last Saturday, I'm pretty sure the problem didn't arise, but it did on Monday evening after driving home from work in the rain...

From the display, indication is the inner RHS (the one next to the front number plate).

I like the idea of a bit of 'percussive maintenance', I'll see if that 'fixes' it next time!

It's a bit of a pest that the sensor has failed (or at least, its weather sealing has) just out of warranty.

**wai** · 15-10-2014, 11:16 AM

Originally Posted by k_rider

It's a bit of a pest that the sensor has failed (or at least, its weather sealing has) just out of warranty.

That should not be an issue. The dealers and VW will always try it on, but a component like this should not fail "just out of warranty". There is a reasonable expectation that the sensor should last longer.

Press the issue with VW, and contact Fair Trading if necessary.

**Transporter** · 15-10-2014, 12:02 PM

Hmm, interesting. It could also be said that something poked it, or the high pressure cleaner was used to close damaging the sensor.

So, I wouldn't be jumping on the high horse and shouting the "Fair Trading" thing.

**wai** · 15-10-2014, 07:04 PM

Originally Posted by Transporter

Hmm, interesting. It could also be said that something poked it, or the high pressure cleaner was used to close damaging the sensor.

So, I wouldn't be jumping on the high horse and shouting the "Fair Trading" thing.

Surely it could be argued that something fitted to a bumper should able to withstand the odd bump (which would be visible), and should be able to withstand some water pressure from a cleaner? It would be another thing altogether if the sensor was mounted inside the vehicle away from the elements.

**k_rider** · 15-10-2014, 10:35 PM

Yeah, I'd certainly aim for the 'gentle' approach with the dealer. And I'd have to agree something like this should last pretty much for the life of the car under 'normal' circumstances (ie not being hit or had high pressure jets of water aimed at it).

FWIW, it's never been hit, to my knowledge anyway. There's always the chance it's been bumped whilst parked, but other damage would be evident. I've also never used a high pressure cleaner on the car, I'm always worried that the jet will find a stone chip or some such and start lifting paint! I've also taken care to avoid directly spraying at the PDC sensors even with a normal hose nozzle, as I was never sure how well sealed they are.