GrahamS

Hi All

A few days ago I was driving my 2010 4.2 TDI (60,000 miles) in busy stop-start traffic using ACC when all of a sudden as the car came to a halt (due the car ahead stopping) the parking brake was applied and the ACC dashboard light turned red to indicate it had stopped operating. There wasn’t anything abnormal about the situation, apart perhaps from the extreme (for the UK, lol) outdoor temperature of about 35 deg C. I’ve had ACC stop once before (not in extreme temperature) and an engine off/on has reset the ACC but not this time.

On engine startup I had the ACC and Audi Braking Guard: Unavailable message in the dash and VCDS was reporting (amongst many other faults that were related):

Address 13: Auto Dist. Reg > Cannot be reached

Various Modules > 4709 - No Communications with Cruise Control (Front) Distance Sensor

Address 46: Central Conv. (J393) > 01319 - Control Module for Distance Control (J428) : 004 - No Signal/Communication

The faults wouldn’t clear and I couldn’t find any blown fuses. Thinking it was a bit odd that ACC should suddenly give up the ghost I was wondering if it would be possible to 'reboot' everything – perhaps by disconnecting the battery. (Sounds crazy but after a battery change just after purchasing the car several features [such as cornering headlights] started working that previously didn’t.)

Then I remembered that the MMI had some settings that could be tweaked under Driver Assistance. Nothing useful in ACC itself but under braking guard there is the possibility to turn it off. Which I did. And back on again. And lo and behold….ACC and Braking Guard restored to full working order and all faults able to be cleared!!!!!!!

I’m obviously posting this to hopefully help someone in the future but for interest’s sake has anyone had a similar experience with 'turning it off and on again' or can shed any light on what might have been going on behind the scenes? Cheers!

A8L_New_England

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How's your battery? How old? Maybe load test it after a good hot drive.
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GrahamS

Only a year old, so I'd hope in good condition. Are you thinking this might have been the cause of the ACC to stop working whilst in use?

A8L_New_England

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With all those codes, I'd double check it regardless of age. Quick, simple and free diagnostic.
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GrahamS

Thanks - I'll check that out!

For reference for anyone troubleshooting this on their own car, the ACC suddenly stopping working triggered faults in all these modules at the same time:

01-Engine -- Status: Malfunction 0010
03-ABS Brakes -- Status: Malfunction 0010
11-Engine II -- Status: Malfunction 0010
31-Engine other -- Status: Malfunction 0010
13-Auto Dist. Reg -- Status: Cannot be reached 0100
15-Airbags -- Status: Malfunction 0010
17-Instruments -- Status: Malfunction 0010
19-CAN Gateway -- Status: Malfunction 0010
34-Level Control -- Status: Malfunction 0010
46-Central Conv. -- Status: Malfunction 0010
53-Parking Brake -- Status: Malfunction 0010
85-On Board Cam. -- Status: Malfunction 0010
8B-Adaptive Cruise 2 -- Status: Malfunction 0010
8E-Image Processing -- Status: Malfunction 0010
8F-Pretens. Frt Left -- Status: Malfunction 0010
90-Pretens. Frt Right -- Status: Malfunction 0010

The good news is that I managed to completely clear all these faults once the ACC had been reset.