Break Servo Restricted

Faults and Technical chat for the Audi Q4
TheSarge
Posts: 48
Joined: Thu Aug 12, 2021 5:57 am

Post by TheSarge » Fri Jan 28, 2022 8:10 am

Currently sat at a service station with the above fault code and total breaks failure waiting for Audi Assist to arrive :roll:

TheSarge
Posts: 48
Joined: Thu Aug 12, 2021 5:57 am

Post by TheSarge » Fri Jan 28, 2022 8:38 am

Fair play to Audi Assist, here in 30 mins and being diagnosed, car is reporting the servo module has failed

Tony
Posts: 243
Joined: Wed Nov 03, 2021 9:27 am

Post by Tony » Sat Jan 29, 2022 9:32 pm

Were they able to fix it or as it in service?

ryanMcLion
Posts: 5
Joined: Sat Jan 29, 2022 10:41 pm

Post by ryanMcLion » Sat Jan 29, 2022 10:46 pm

Hi,

Just searched and found this forum tonight and saw your post.

My wife's Q4 brakes failed last week. She said they completely failed and the car just rolled out of a hand car wash forecourt. She said the pumped the brakes but nothing happened and it juddered like abs but kept rolling. She had to quickly hit the start stop button to stop the car and then then the message "brake failure contact workshop" came up. The car then went back to normal.

This was confirmed by Audi that there was a brake failure on the car fault log but they can't tell us why and told us "to come back if it happens again".

We're now refusing to drive it until I have some reassurances that it's ok!

Is what happened to you similar to the above?

TheSarge
Posts: 48
Joined: Thu Aug 12, 2021 5:57 am

Post by TheSarge » Sun Jan 30, 2022 12:09 am

That's exactly what happened to mine but in a little less of a dramatic situation as I was moving out of a parking space. The peddle juddered like ABS was happening and then I had a series of faults appear on the dash. I did get it rolling back but had to force the car into park to stop it.

I will keep you updated as the car is with Audi at the moment, the breakdown guy said the car was reporting a problem with the break servo so let's see what they say!

hugodoodle
Posts: 61
Joined: Wed Oct 06, 2021 4:35 pm

Post by hugodoodle » Sun Jan 30, 2022 8:11 am

If this happens again, press and hold the parking brake button. The response from the vehicle will depend upon the failure state of the electronic brake booster and ABS/ESC system.

If it is not in full failure mode, it will apply the hydraulic brakes to deliver 0.5g deceleration and the slow the vehicle to a stop. If the system is in failure mode, the vehicle will instead apply the electronic parking brake and modulate it (avoiding rear wheel lock) to slow the vehicle to a stop (probabably at 0.3g).

A normal braking system on a passenger vehicle must, by design must be independant of the parking brake system. The parking brake system is the final line of redundancy to provide deceleration in the event of primary brake failure.

You are right on insisting further diagnosis from Audi - a primary brake failure is a critical safety issue and they should investigate with tech support from Audi and provide you with the confidence that they understand the issue and have resolved it.
Q4 50 Quattro Edition 1 C+S

ryanMcLion
Posts: 5
Joined: Sat Jan 29, 2022 10:41 pm

Post by ryanMcLion » Sun Jan 30, 2022 8:38 am

Hi Sarge

Thanks for the message. Have Audi taken it away?

They have refused to take my car and both mechanics have said they can't see any issues but haven't any idea what caused the issue.

TheSarge
Posts: 48
Joined: Thu Aug 12, 2021 5:57 am

Post by TheSarge » Sun Jan 30, 2022 9:10 am

Yeah, they recovered it back to my local Audi dealer so now awaiting a call from them. The Audi Assistance guy did a roadside diagnosis and there were several fault codes including one mentioning servo comms fault.

Will let you know once they come back to me, in the meantime Audi have booked me a rent a car, a ridiculous Merc GLE!

ryanMcLion
Posts: 5
Joined: Sat Jan 29, 2022 10:41 pm

Post by ryanMcLion » Wed Feb 02, 2022 8:22 pm

TheSarge wrote:
Sun Jan 30, 2022 9:10 am
Yeah, they recovered it back to my local Audi dealer so now awaiting a call from them. The Audi Assistance guy did a roadside diagnosis and there were several fault codes including one mentioning servo comms fault.

Will let you know once they come back to me, in the meantime Audi have booked me a rent a car, a ridiculous Merc GLE!
Hey sarge. Just wondered how you had got on?

I'm taking my Q4 in tomorrow.

TheSarge
Posts: 48
Joined: Thu Aug 12, 2021 5:57 am

Post by TheSarge » Fri Feb 04, 2022 3:12 pm

Hi,

Yeah picked my car up yesterday but Audi were left scratching their head. They cleared the faults and checked the mechanics but could not find anything wrong so I guess I'm in a similar situation. I have taken the car back but I'm sure it will rear it's head again!

They have assured me that any issue on the road won't leave me with zero breaks and the emergency crash thing is totally independent so will stop me crashing into anything if the worst were to happen!

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