A7 intermittent not starting/cutting out and shutting down whilst driving

[X000-000X]

I thought I'd post my issue here on the off chance anyone else has experienced similar issues and may know the solution.

 

So month or so ago, my A7 had been left standing for 3 weeks, went to use and wouldn't unlock upon further investigation there was no power at all to the vehicle, suspected dead battery - I've owned the car close to 2 years, never had the battery replaced so purchased a replacement (a Yuasa battery, which happened to be the same a the one that was in use).

 

Once the battery was replaced car sprung to life, life was good, rightly or wrong following advised regarding battery replacement I used a Carista ODB2 to change the last digit of the serial number to code the battery (also cleared 27 or so faults which appeared to be related to a dead battery).

I used the car a couple of times on 30 minute+ journeys, left the car sat for 3 days drove went to drive again and it unlocked with no issue but was unable to start, the dash wouldn't light up, then wasn't able to lock or do anything which required power (I'm unsure if the lights in the boot were working), removed the battery charged it with an AGM mode charger, perhaps 26hours to complete the charge, installed battery, again everything worked, drove a couple of times leaving no more than a 2 or 3 day gap, I drove again and left it parked for 2-3 hours, went to unlock but only the front passenger unlocked from the fob, wouldn't start and all I was able to do was lock/unlock front passenger door and operate just that electric window (the automatic window dip on opening the door worked) - tried a jump start but still nothing, noticed both connectors on the battery terminals were lose, removed the negative and re-connected it tightened them up - car was again running, OBD2 had same errors as before, battery charge level slowly increased from the 64% it was showing.

Drove the car again a couple of times, left sat for 2 days - unlocked (all doors) with no issue but was unable to start, the dash wouldn't light up, the boot lights were the only thing working - I removed the negative terminal and reconnected and dash lit up immediately and was able to start and use. At this point booked in with a specialist to diagnose (2.5 week wait)

No further issues in the 1.5 weeks which followed then was driving back from a short trip (had driven a long journey the night before), and what sounded like a popping sound came from behind me - car lost power fortunately I was able to coast into a parking space, multiple errors displayed one after another, TPMS failure, steering failure, braking failure, etc and after the last error it shut itself down and again only front passenger door (and boot lights) had power, couldn't start so I thought I'd chance disconnecting the terminals (I perhaps did this 5 or 6 times and then was able to start the car again, cleared all errors and continued the journey.

I had to get home, so opened the boot from the FOB with no issue, but car wouldn't unlock or start - so usual shenanigans with the battery terminals and was running again, car completed 47miles out of my 50 mile journey when power cut out, was able to get to a safe(ish) place to stop power to passenger door and boot lights (and rear hazards worked (drivers door wing indicator wasn't working), tired the same battery trick but seems as luck had run out after 30 minutes I gave up and called RAC - no manner or things tired could restore power after 30 minutes or so decided it would need to be recovered, no power to release handbrake or take out of park so couldn't be towed - I put the tools and spare wheel back it in preparation of recovery and as was tightening the spare wheel nut the dash sprang to life and car started - this time there is a message along the lines of "stop start has failed, please take to workshop" cleared all errors and after turning off and on, the stop start error has remained, whether this was the issue all along and it's finally failed remains to be seen.

I've still got a week to go before the car is booked in so very reluctant to drive it in the meantime in case it breaks down somewhere considerably more dangerous to stop but also aware that the battery will possibly be flat as before.

 

Has anyone experienced similar issues or have any thoughts on what could be the issue?

 

Cheers,

Mike

 

[NJP10]

10 minutes ago, X000-000X said:

I thought I'd post my issue here on the off chance anyone else has experienced similar issues and may know the solution.

 

So month or so ago, my A7 had been left standing for 3 weeks, went to use and wouldn't unlock upon further investigation there was no power at all to the vehicle, suspected dead battery - I've owned the car close to 2 years, never had the battery replaced so purchased a replacement (a Yuasa battery, which happened to be the same a the one that was in use).

 

Once the battery was replaced car sprung to life, life was good, rightly or wrong following advised regarding battery replacement I used a Carista ODB2 to change the last digit of the serial number to code the battery (also cleared 27 or so faults which appeared to be related to a dead battery).

I used the car a couple of times on 30 minute+ journeys, left the car sat for 3 days drove went to drive again and it unlocked with no issue but was unable to start, the dash wouldn't light up, then wasn't able to lock or do anything which required power (I'm unsure if the lights in the boot were working), removed the battery charged it with an AGM mode charger, perhaps 26hours to complete the charge, installed battery, again everything worked, drove a couple of times leaving no more than a 2 or 3 day gap, I drove again and left it parked for 2-3 hours, went to unlock but only the front passenger unlocked from the fob, wouldn't start and all I was able to do was lock/unlock front passenger door and operate just that electric window (the automatic window dip on opening the door worked) - tried a jump start but still nothing, noticed both connectors on the battery terminals were lose, removed the negative and re-connected it tightened them up - car was again running, OBD2 had same errors as before, battery charge level slowly increased from the 64% it was showing.

Drove the car again a couple of times, left sat for 2 days - unlocked (all doors) with no issue but was unable to start, the dash wouldn't light up, the boot lights were the only thing working - I removed the negative terminal and reconnected and dash lit up immediately and was able to start and use. At this point booked in with a specialist to diagnose (2.5 week wait)

No further issues in the 1.5 weeks which followed then was driving back from a short trip (had driven a long journey the night before), and what sounded like a popping sound came from behind me - car lost power fortunately I was able to coast into a parking space, multiple errors displayed one after another, TPMS failure, steering failure, braking failure, etc and after the last error it shut itself down and again only front passenger door (and boot lights) had power, couldn't start so I thought I'd chance disconnecting the terminals (I perhaps did this 5 or 6 times and then was able to start the car again, cleared all errors and continued the journey.

I had to get home, so opened the boot from the FOB with no issue, but car wouldn't unlock or start - so usual shenanigans with the battery terminals and was running again, car completed 47miles out of my 50 mile journey when power cut out, was able to get to a safe(ish) place to stop power to passenger door and boot lights (and rear hazards worked (drivers door wing indicator wasn't working), tired the same battery trick but seems as luck had run out after 30 minutes I gave up and called RAC - no manner or things tired could restore power after 30 minutes or so decided it would need to be recovered, no power to release handbrake or take out of park so couldn't be towed - I put the tools and spare wheel back it in preparation of recovery and as was tightening the spare wheel nut the dash sprang to life and car started - this time there is a message along the lines of "stop start has failed, please take to workshop" cleared all errors and after turning off and on, the stop start error has remained, whether this was the issue all along and it's finally failed remains to be seen.

I've still got a week to go before the car is booked in so very reluctant to drive it in the meantime in case it breaks down somewhere considerably more dangerous to stop but also aware that the battery will possibly be flat as before.

 

Has anyone experienced similar issues or have any thoughts on what could be the issue?

 

Cheers,

Mike

 

Hi Mike

sorry can’t say I have and I hope don’t either, sounds like a right nightmare!! 
Just out of interest what year is your A7?

[X000-000X]

Yeah, it certainly is, could deal with the battery needing to be disconnected/reconnected to start it for another week but not potentially stopping on a motorway.

It's 2013 & the 3L Diesel variant.

[Magnet]

Hello Mike,

To try to make this short and simple:- 

Charge the battery overnight, and get its efficiency checked on sophisticated equipment. 
Check all connections associated with charging/ starting circuits  ( loose battery terminal concerns me since recent new battery - why?) 

Check alternator output. 
Check for ( possibly significant?)parasitic drain. 
A good auto electrician should be able to perform all these checks in 1 hour’s labour. 
If it were mine, that’s what I would be doing. 
Kind regards,

Gareth. 

[X000-000X]

4 minutes ago, Magnet said:

Hello Mike,

To try to make this short and simple:- 

Charge the battery overnight, and get its efficiency checked on sophisticated equipment. 
Check all connections associated with charging/ starting circuits  ( loose battery terminal concerns me since recent new battery - why?) 

Check alternator output. 
Check for ( possibly significant?)parasitic drain. 
A good auto electrician should be able to perform all these checks in 1 hour’s labour. 
If it were mine, that’s what I would be doing. 
Kind regards,

Gareth. 

Hi Gareth,

Thank you for you message.

I've currently got the original battery on charge, as planning to swap the battery over and see if that makes any difference and then as you've suggested I'll charge the new battery up and then drop everything off to the Audi Specialists next week (earliest booking I could get). 

It was the car connection to the battery poles which were loose, I hadn't tightened them up properly (just incompetence on my part) - the terminals on the battery itself are sound.

Using the Carista app and bluetooth ODB2 the alternator appears to be working, I get an output of between 14.5v and 15v (and the battery does gain charge) - I can only assume that's accurate enough to rule that out as that's what the car is giving via the diagnostic port, but I agree does need to be performed by someone who knows what they are doing.

I did start to look into the parasitic drain angle, I've tried disconnecting the negative and measure across that and positive with a voltmeter, the reading started on about 13v and went down to 0v but I've not check across each fuse checking for a current in milli-amps, however, the battery (again measure using Carista) has been as low as 64% car started first time and as high at 79% and not started - this suggests there is no correlation between battery charge and whether or not it starts, in the latter example, I removed the negative connection and re-connected it no more than 30 seconds later and then everything worked - I'm not 100% sold on that being accurate enough to make a determination, but also the battery charge dropping by around 6% per day feels somewhat on the high side and even if the issue isn't caused by parasitic drain there perhaps is a secondary issue of parasitic drain.

I'll double-check when I drop it off that both of these will be checked.

Cheers,

Mike

 

[Stevey Y]

28 minutes ago, X000-000X said:

Hi Gareth,

Thank you for you message.

I've currently got the original battery on charge, as planning to swap the battery over and see if that makes any difference and then as you've suggested I'll charge the new battery up and then drop everything off to the Audi Specialists next week (earliest booking I could get). 

It was the car connection to the battery poles which were loose, I hadn't tightened them up properly (just incompetence on my part) - the terminals on the battery itself are sound.

Using the Carista app and bluetooth ODB2 the alternator appears to be working, I get an output of between 14.5v and 15v (and the battery does gain charge) - I can only assume that's accurate enough to rule that out as that's what the car is giving via the diagnostic port, but I agree does need to be performed by someone who knows what they are doing.

I did start to look into the parasitic drain angle, I've tried disconnecting the negative and measure across that and positive with a voltmeter, the reading started on about 13v and went down to 0v but I've not check across each fuse checking for a current in milli-amps, however, the battery (again measure using Carista) has been as low as 64% car started first time and as high at 79% and not started - this suggests there is no correlation between battery charge and whether or not it starts, in the latter example, I removed the negative connection and re-connected it no more than 30 seconds later and then everything worked - I'm not 100% sold on that being accurate enough to make a determination, but also the battery charge dropping by around 6% per day feels somewhat on the high side and even if the issue isn't caused by parasitic drain there perhaps is a secondary issue of parasitic drain.

I'll double-check when I drop it off that both of these will be checked.

Cheers,

Mike

 

Hi it sounds as if it could be something to do with the rear CCM/ECU maybe a wire gone through or corrosion of the terminals on the unit itself that will cause all sorts of weird and wonderful problems, only gone for this theory based on the battery voltages you stated and the fact it started when you replaced the spare wheel, it seems movement is causing a make and break situation.

Steve. 

[X000-000X]

On 5/2/2022 at 7:55 PM, Stevey Y said:

Hi it sounds as if it could be something to do with the rear CCM/ECU maybe a wire gone through or corrosion of the terminals on the unit itself that will cause all sorts of weird and wonderful problems, only gone for this theory based on the battery voltages you stated and the fact it started when you replaced the spare wheel, it seems movement is causing a make and break situation.

Steve. 

Only thing I was able to find was when I shook the block attached to the positive terminal on the battery, the L shape one with the two chunky red cables on a connector labeled as 150A and a really thick cable (perhaps 2 inches wide) the car completely cut out, it didn't generate all the same errors as before, perhaps as I wasn't driving it?, I tighten up the nuts on those connectors, they weren't what I'd consider loose but there was definitely more play than there is now and I wasn't able to replicate the problem after. I'm not sure I buy into it being a loose connection there (as battery shouldnt really be in play at that point, though if its arcing I guess could be problematic, possibly I disturbed it enough to work a bit loose when changing the original battery (supports the starting when the spare wheel was put back though). I've not been able to locate anything looking corroded or anything loose.

I've not driven the car since 2nd but have started it a numbet of times and its started each time with no issue.

Car is going in tomorrow so hopefully will have, albeit potentially expensive (if its the ccm that needs replacing) fix.

[Steve Q]

7 hours ago, X000-000X said:

Only thing I was able to find was when I shook the block attached to the positive terminal on the battery, the L shape one with the two chunky red cables on a connector labeled as 150A and a really thick cable (perhaps 2 inches wide) the car completely cut out, it didn't generate all the same errors as before, perhaps as I wasn't driving it?, I tighten up the nuts on those connectors, they weren't what I'd consider loose but there was definitely more play than there is now and I wasn't able to replicate the problem after. I'm not sure I buy into it being a loose connection there (as battery shouldnt really be in play at that point, though if its arcing I guess could be problematic, possibly I disturbed it enough to work a bit loose when changing the original battery (supports the starting when the spare wheel was put back though). I've not been able to locate anything looking corroded or anything loose.

I've not driven the car since 2nd but have started it a numbet of times and its started each time with no issue.

Car is going in tomorrow so hopefully will have, albeit potentially expensive (if its the ccm that needs replacing) fix.

Keep us posted on how you get on. I've been putting off a CCM change on my A6 for a while. 

[X000-000X]

So I thought I'd give it a few days before updating so as not to jinx it but the problem appears to be cured. It appears the black lead connecting to the positive terminal may not have been making good contact, the specialists were able to exactly replicate the symptoms by just removing it, the end of the 150A flat fuse below it was looking a bit sorry for itself so they cleaned that up and touch wood it's been fine since. Battery is good and drain after 30mins is 0.01A. I also noticed yesterday the engine fan was working (hadn't realised I'd not heard that recently if that makes sense), I did check the car about an hour later to make sure it had definitely stopped.

They advised the next step should the issue persist is start dismantling the car to trace where that lead goes as after it disappears into the body of the car, they estimated 4-5 hours labour and were reluctant to charge me for that if it doesn't need to be done.

Probably just in my head but it feels nicer to drive and more responsive.

Sorry to hear about you needing a replacement CCM, that's one invoice I'm dreading

[Steve Q]

1 hour ago, X000-000X said:

So I thought I'd give it a few days before updating so as not to jinx it but the problem appears to be cured. It appears the black lead connecting to the positive terminal may not have been making good contact, the specialists were able to exactly replicate the symptoms by just removing it, the end of the 150A flat fuse below it was looking a bit sorry for itself so they cleaned that up and touch wood it's been fine since. Battery is good and drain after 30mins is 0.01A. I also noticed yesterday the engine fan was working (hadn't realised I'd not heard that recently if that makes sense), I did check the car about an hour later to make sure it had definitely stopped.

They advised the next step should the issue persist is start dismantling the car to trace where that lead goes as after it disappears into the body of the car, they estimated 4-5 hours labour and were reluctant to charge me for that if it doesn't need to be done.

Probably just in my head but it feels nicer to drive and more responsive.

Sorry to hear about you needing a replacement CCM, that's one invoice I'm dreading

Glad its all resolved 🤞 let's hope it stays that way! 

My A6 is sentimental so I consider the cost worth it. When I get it done I'm going to get a specialist to do it and move it from off the floor to another location to protect it.