I have an Audi A8 D3/4E, I have an issue with the parking sensor not working anymore. It started with the parking sound always sounding in the back even if I were not close or nearby to any object. Now the parking sensor is not working at all. When I put the car in reverse, the parking sensor light inside the car is just blinking green.

 

VCDS scan will help you to find what's wrong.

 

Funny you mention this - the wife's 2009 A8L started doing the exact same thing. I put it down to the heavy rain we had in the UAE yesterday, this car tends to play up when it sees water. No probs with the S8 and it got equally soaked.

I'm gonna wait a couple of days for everything to dry out and see if it goes back to normal. If not, I'll get out the VCDS and post back.

 

If it helps the opening poster: after a day of drying out, the parking sensors returned to normal on my wife's car. Managed to do a quick scan just for interest, looks like water got in for sure. Sorry if that doesn't help, but do you have access to VCDS? As above, might give you a clue which of the sensors is faulty, or if it's a module. I guess if one individual sensor fails the whole system is inhibited to prevent false indications. With my wife's parking, that would lead to inevitable bumps and dents...

Wednesday,01,March,2017,14:24:53:06900
VCDS -- Windows Based VAG/VAS Emulator Running on Windows Vista x86
VCDS Version: 17.1.2.1
Data version: 20170131 DS267.1
Ross-Tech: Home


VIN: License Plate: 96543
Mileage: 87950km Repair Order:



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Address 76: Park Assist Labels: 4E0-910-283.lbl
Control Module Part Number: 4E0 910 283 D HW: 4E0 919 283 C
Component and/or Version: Parkhilfe 8-Kan H12 0050
Software Coding: 0321008
Work Shop Code: WSC 131071 1023 2097151
VCID: 244796CDE7C10B61A6-8070
2 Faults Found:

01628 - Sensor for Parking-Aid; Front Mid-Left (G254)
009 - Open or Short to Ground - Intermittent
Freeze Frame:
Fault Status: 00101001
Fault Priority: 3
Fault Frequency: 2
Reset counter: 103
Mileage: 87807 km
Time Indication: 0
Date: 2017.02.27
Time: 07:43:01

01628 - Sensor for Parking-Aid; Front Mid-Left (G254)
004 - No Signal/Communication - Intermittent
Freeze Frame:
Fault Status: 00101001
Fault Priority: 3
Fault Frequency: 2
Reset counter: 103
Mileage: 87807 km
Time Indication: 0
Date: 2017.02.27
Time: 07:43:01


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Address 76: DTCs cleared

 

I scanned my car today for the rear sensor issue. NO fault codes. But I went into the measured values and found the sensors were reading (left to right, rear)
25cm 255cm 255cm 255cm (I think units are cm)

So obviously the left most one is pooched somehow. Have an EBAY one coming I think it was like $20 or so.