A7 intermittent non starter problems keyless fobs

[MB2208]

Please can anyone advise on the following issues which have suddenly started on our A7 .

Had the vehicle 18 months with no major issues but the following events have happened and now at a loss and worry how to proceed further:

Approx 6 weeks ago the dash showed “Low tire pressure”

checked and inflated the tires where necessary - and stored the readings - as previously done without issues.

Following day - engine would. Not start - dash show “Press brake pedal to start engine”

Remote works for looking/unlocking, radio and all other electrics work.

dash reading still showed “Low tire pressures”

Stored the readings again - but no success.

The Dash then  shows “Stabilisation program fault! See owners manual”

I have replaced the batteries in key fobs, also main battery located in boot.

Sometimes after showing either of the remote fobs in front of the “sensor” on the dashboard - a red light flashes and the car will sometimes start - but not always.

Once the car is running - its fine - no other issues - but its causing stress now as I cannot rely on the car starting every time.

2 x Local garages have performed diagnostic tests - with nothing showing (apar from initially for the main battery - now replaced)

This has also happened after the car has been on a good run - so not even down to low power/Horst journeys etc.

Any guidance would be appreciated 

Many Thanks

[Stevey Y]

Hi sorry to hear of your problems, you are heading in the right direction with the battery replacement keys/main, so the only question I would ask the garage who fitted the main battery is if its A, the correct battery for your model B, was it recoded to the vehicle so it registered the new unit, I have found through experience with the later German vehicle that the electronics are not happy with voltage spikes or any radical changes in voltage draw.

The other thing I have discovered is that the generic diagnostic software will read a lot of problems on most cars mostly obvious problems like the main battery but completely miss underlying problems especially with the electronics on Audis, this is not the garages fault as they have to spend a fortune on a generic code reader that covers all models they work on, therefore might I suggest you source an Audi specialist as they will have the manufacturer specific software that will search in depth into the various control modules and will throw up any underlying faults which don't otherwise make themselves obvious. 

The reason I asked about battery coding is that if you just put the new battery straight in, yes it all works wonderfully but the problem is the smart charge system will still be trying to charge the new battery at the same rate as the old knackered unit because it has not been advised of the new unit, this can cause as many weird electrical problems as a failing battery.

Regards Steve.

[MB2208]

Hi Steve,

 

Thak you for your advice. Greatly appreciated.

In respect of the correct battery - I assume so as its the regular garage who usually services the car, and he ordered based on the registration number etc.

For recoding the battery - they did come and fit the battery at home -( as it wouldn’t start to get to the garage ) with this in mind - is there something they should have done then to recode the new battery ? Or will I need to take it to a Audi specialist to now check/compete this Action?

Sorry to ask a basic question - but this particular element I assumed the garage would have automatically done.

(They did do another diagnostic check after the problem re-occurred , but as there were no fault codes showing - they said everyone they sought advice from wouldn’t get involved due to the complex nature of the Audis etc 🙈)

The nearest Audi dealership would be over 15 miles from us - and as we know they are not going to diagnose for free, and we are not in a position to start “process of eliminations” at Audi prices 

 

Thanks again fr your guidance 

Michelle

[Stevey Y]

Hi when they fitted the new battery did you see them sit in the car afterwards with a laptop or similar and fiddle about with it that would have been the recoding, I was definitely not suggesting that you opened a major financial artery at an Audi dealers those guys are legalised highway men preying on the average car owner who often as not have no clue as to whats going on, hence these forums.

As for the complexity of the Audis any newer car will be complex if you don't have the equipment to plug in and read them properly, I was thinking more along the lines of an independent specialist or better still a mobile diagnostics company as these guys normally have excellent software for every vehicle and charge an initial fixed payment for a diagnosis with a printout so at least even if you cant understand it a garage will if they are any good, I used one of my local mobile diagnostic companies for a few years they were good, even try asking on social media if any one has VCDS and would not mind scanning your car for a small fee, its worth a try and if you were not so far away most of the guys on this forum including myself who have VCDS if they lived near would have no problem helping you, as I said thats what forums like this are about. As for local garages assume nothing as its a dangerous hobby and their get out is, you didn't ask us to do that.

Regards Steve.

[MB2208]

Hi Steve

 

Thank you so much your advice is invaluable.

I don’t recall the garage actually using a laptop or similar device after installing the new battery - so this could be a good starter for me to query.

There is a mobile diagnostic company I have just found who are “specialists in Audi” so i  also contact them after the weekend and enquire - based on your guidance.

I will keep you posted - and Thank yu again.

Michelle

[Stevey Y]

20 hours ago, MB2208 said:

Hi Steve

 

Thank you so much your advice is invaluable.

I don’t recall the garage actually using a laptop or similar device after installing the new battery - so this could be a good starter for me to query.

There is a mobile diagnostic company I have just found who are “specialists in Audi” so i  also contact them after the weekend and enquire - based on your guidance.

I will keep you posted - and Thank yu again.

Michelle

Well done, the mobile Chappy is bound to be more knowledgable being as they specialise in your make of vehicle, voltage spikes are the Bain of any electrical system especially on cars they can trigger the most random problems, my money is on a lack of recoding so the Body Control Module has thrown a fit because its found something it doesn't like, but please keep us informed even if you only get as far as the codes as some where on this forum is the answer so at least you can go to a garage armed with the right information and they won't try and kid you its something else.

I wish you luck, Steve.

[MB2208]

Hi Steve

Following your advice I have now managed to get the following info from the garage who did the battery:
The new battery fitted is a Platinum AGM Stop-start Batterry - based on the needs of the model and registration number.

 

He advised he did not “recode” with the new battery as its not needed to be done previously , and also he felt as the fault was already in existence with the old battery it would settle itself with the new one.

His advise was also that - if t was the new battery needing coding - the auto “Stop-start” button would not kick in when the car is running/warmed up.

(This does still kick in when on a run - although I always choose to switch it off )

 

So, based on your advice _ Ive now  spoken with the 2nd garage who actually try to do diagnostics last week (and replaced the key fob battaries for me) and he has the VCDS equipment your referring to - so is happy to apply this and try recoding to see if that resolves the problem. (Going on Friday to see him)

If that fails - then I will need to contact the mobile diagnostics mechanic mentioned earlier and get him to come out and evaluate.

I will keep you informed and again - appreciate everyone guidance and patience.

Regards Michelle

 

[Stevey Y]

Hi Michelle I am amused at garage number ones explanation for why you don't have to recode the battery its BULL as most of the cars I have owned since 2009 have had to have the battery monitor/counter reset when you fit a new unit, this is how the charging system works, the battery is coded to the car from new as the battery gets older it requires more charge from the alternator this is supervised by what is known as a smart charge system  this will keep upping the voltage as it senses the battery becoming less able to maintain its optimum charge therefore it requires charge more often, this function ceases to be of any use once the battery cells become incapable of holding more than 68% of its charge therefore it makes it impossible to start as this draws the most amperage which in theory will drain whats left of the battery power quickly and cause the charging system to work far harder to catch up which at that point it never will, so it goes into its own protection mode, won't start, everything else will work until the battery is depleted.

Now if you replace the battery without recoding yes everything will work but the smart charging thinks the battery has risen from the dead and carry on trying to charge at the higher rate which causes problems with the electrics, when recoding the software system VCDS will ask for information as to the make of the battery but mainly what amp hour and the cranking voltage and as long as its a couple of volts/amps  within the original specification you can tell it that the replacement is the same as the old battery which makes the smart charge system happy as it now knows it has a new unit and this will only require less charge as it will have good storage capabilities, settling down will never happen as the charging system is not sophisticated enough to have self analysis capabilities so you have to tell it, the second guy seems a more tuned in proposition, I wish you luck.

Steve.

[MB2208]

Thanks Steve,  I will keep fingers crossed and let you know 

 

Best Regards

Michelle

[MB2208]

Hi everyone, 

Just a quick update  - unfortunately the recoding of the battery has not solved the non starting issue.

 

The garage recoded everything as suggested - and the equipment highlighted the fact that we had attempted to start the car almost a dozen times first thing to get started - but did not identify what the cause was or any “actual faults” 

So - back to the starting base again .

Thank you for your advice - it was appreciated though 

Michelle

[Stevey Y]

Hi Michelle, sorry to hear of your continuing problem but at least the recode has eliminated the battery as the source of the problem, based on your first post does the press the brake pedal to start keep appearing even when the car won't start? if so the pedal switch may be the problem as this lets the ECU know when its safe to start but I cant think why that has not thrown a code up but instead counted all the start failures, only thing I can suggest is try the mobile diagnostic as it is probable that they have a more in depth software that will expose the real problem.

Regards Steve.

[MB2208]

Hi Steve 

Just wanted to update you on the saga of the car.

We did a change of the sensor on the brake pedal - which was a good idea - Thank you.

Unfortuately this did not resolve the problem (although it was pretty worn so at least its replaced now)

The diagnostics is showing a faulty on the ECU , so the garage is trying to look into the possibility of the Unit being refurbished - with a lifetime warranty, to try to help reduce the costs etc. We’re praying this will be a manageable option - as of course the nightmare costs of a new ECU will be totally gutting.

 

Thanks again for your guidance with this issue - it was appreciated.

Michelle 

[Stevey Y]

Hi Michelle, sorry about the ECU fault it was the last item I would have thought of, but on a positive note if the ECU is still talking to the diagnostics it a going proposition and should be repairable there are companies all over the UK that specialise in this type of repair and they are normally very successful in repairing these units I use one in Kent and they have saved me a fortune over the years, please let me know how you end up.

Regards Steve.

[MB2208]

Thanks Steve , should hopefully know more early next week. We’ve left the car with the garage now .