I have just got a q5 2015 se model.

It has rear sensors fitted but the mmi option is in grey and not red. Where to start fault finding please.

 

Hello Jon,

Probably down to one of the sensors being faulty, but regrettably it’s likely to need diagnostics to home in on the culprit. 
Kind regards,

Gareth. 

Yeah I thought so. Many thanks 

You don’t need to get a diagnostic. You can find the faulty sensor by putting the car in reverse. The car will activate the sensors. Go round each sensor on the car and put your ear to them. The good ones will make a clicking sound. The bad ones won’t. 
 

Recently did this on my Q5 and found 2 dead sensors. Replaced, and all worked spot on from then. 
 

There is a YouTube video out there that explains in more detail. But that’s the general gist. 

Yeah. I tried the listening to each sensor and figured out the dead one.

Thanks 

👍

Regrettably, never worked on mine! 

Apparently on certain cars you can press the sensor in with your finger to test if ones faulty. Whether this is true I'm not sure. 

All fixed. Dealer sorted it at no cost to me.

Thanks Jon. So what was the fix? 
Kind regards,

Gareth. 
p.s. Re. these YouTube suggestions of listening, WD40 etc. etc. Has anyone actually identified the failed sensor by these methods - rather than assuming the procedure works? As I say, never worked for me, so would genuinely be interested to hear if they have actually worked for some. 

For demo purposes I disconnected one sensor.

This results in no display on the MMI, flashing parking sensor button and no functionality. 
 

So, pop the car in R, the parking sensor button will flash, there will be no display, go round the car and listen. Use your phone if your struggling to hear anything, it shows up better on a recording. 
 

I’ve done a billy basic video. Don’t judge. 😄

Glad you got sorted 🙂