wfroehlich

I need some help here. I have a 2011 S5 that will not start. I press the start button and the gauges sweep, lights come, etc. but the engine will not crank. It almost acts like a dead battery. I have replaced the battery since this issue started and it has seemed to get progressively worse.

Here is the interesting part..... If I connect the VAG-COM to the OBD2 port and do an auto scan for fault codes, it shows me quite a few. Without clearing the codes, just pushing the start button to turn the accessory mode off, open the drivers door, close the door and press the start button again, the car will start and run fine. I thought initially that I had to clear the codes but bypassed that step once and can still start the car. I have attached the VAG-COM report which shows the first fault code as P0688 which is loss of power between the ECM and BCM. I have used other software packages like "Shopkeypro" and "Identifix" and am having little luck on determining what the issue is. A mechanic friend thought that it might be the ECM, but I am not sure as the car runs fine. Once I am able to start the car - usually I can start the car for about 30-45 minutes after going thru the procedure listed above. If I wait a longer period of time, I have to repeat the above procedure to start the car.

Any suggestions on what to check?

AUDIQSS

My 2011 S5 Cab sometimes does the same but fixes itself if I move my key fob in my pocket. It may be that the battery in the fob is weak and needs to be replaced.

epox

did you recode vcds to show it has a new battery, worth a try

mark

epox

did you recode with vcds to show it has a new battery, worth a try

mark

wfroehlich

Mark - that did cross my mind but I am not sure how you go about doing that with the VAG-COM software?

wfroehlich

I used the WIKI on Ross-Tech to figure out how to use the long adaptation to add the new battery information in to the VCDS. The only issue is that the battery is an aftermarket battery so I had to get creative when it came to the part number, serial number, etc. Lets see what happens.

Thanks for your help.

Wayne

wfroehlich

I checked the battery voltage and it is around 3.25 volts. I usually have the key on the passenger seat or even in the socket in the dash - same results. Plus my wives key FOB has the same results.

But thanks for replying.

wfroehlich

Here is a little more of an update. In reading some of the other forums, when installing an aftermarket battery, you can use the existing part number and even the manufacture of the battery but you will need to change the serial number by a couple of digits so that if the car contains a "energy management system" this will create a new log and hopefully resolve the issue that I am experiencing. After making this change - the car started on the first try. Let's see what tomorrow morning brings.

epox

Audi A4 B8 Battery Coding - AudiForums.com

might help half way down

epox

Hi i posted a link showing what you have said but its not appeared , hope its a simple fix and all is good tmro

Mark