S5 TDI 3.0 V6 dead battery issues -drum roll pls.

[Beck123]

Hello, I am in the very exciting process of trying to find out what is wrong with my S5. I recently purchased this car in July, its been with the garage since 01/08/2022 under warranty due to the battery being dead when I've gone out in the morning to drive it. Because of this I'm still using my old Audi A3 to commute in -170k and still going strong. This S5 is 2013 year, 99k on the clock. Basically, because my A3 is getting on a bit I thought I would get another Audi, something a bit larger, and always loved the A5. The S5 for the first week was fine, started perfectly each day, no weird noises, no engine/acceleration lag and I didn't get that weird anxious feeling when I drove it like something was going to blow up. So all good right? No, I go out one morning to drive to work and the car unlocks, the dash lights up, key in ignition and nada. Dash flickers, a light on the dash reads 'battery discharge unless driving' or something along those lines. It won't start. Call out road side, jumps the car, says the battery must just be flat -and don't do short journeys. (My work is commuting down the motorway about 20 miles away from I live). So after work that day I take the car on a long drive for an hour, no stereo on, nothing to cause further drain, lights off etc. Anyway, long story short this issue now keeps happening. Get home, turn the car off, sleep, etc etc, get up for work, go to the car, won't start. However, this doesn't happen every day, it's only intermittent, some days I get lulled into that false sense of ok-ness and then will be at work, having driven the car and the car won't start when I'm due to go home.  So, the battery is new, AGM for start stop, load tested, all ok. Other weirdness -P light stays on dash, possibly due to low battery/drain? -power management issue? Intermittent parking camera fault? Loose wire causing battery drain? The Park light staying illuminated on the dash is weird, even when the car has been off, is locked. So I tried not using the park brake, gear the car into park and leave it on a flat surface. Still has the drain without the P on the dash.  I also wonder if the drain is linked to the parking camera working sporadically?  Below is an export from the AA who I called to change the battery to a Bosch AGM silver, but (and he's the third roadside I've called)  nothing wrong with the battery. Must be something else and didn't change the battery -which was bought in 2022 (came with the car). Also, 2 garages later, VAGCOM, no obvious faults. Back to dealer - Audi specialist and they say the alternator is knackered. And I'm like ....what? If the alternator is knackered and drawing charge overnight and not charging the battery properly why does the car sometimes start after a couple of days of being sat unused? Surely the battery would be dead all the time and need jumping. Also, surely the car would just die down the road if the stereo and lights were on if the alternator was knackered?   Also, why does the stereo turn itself on when the car is off and locked, then I have to unlock it, get back in and push the volume button to turn it off. I'm not convinced it's the alternator, but they are fixing it under warranty so 😕  Anyway- AA fault list below, just to confirm? Comm with reverse camera issue, the camera works intermittently -so possibly a wire/fuse issue. I don't really use this so I can probably disable the camera in the settings? Or will this cause more issues -electrical etc. later? MOST data bus, is that the MMI? Open circuit means current isn't getting through? So maybe a short somewhere? Fuse? Dodgy wiring? Energy management active -due to the flat battery? I'm assuming thats the code for that and not some other control unit issue, please for the love of....  Sorry, the only way I'm interpreting the below is through google and wikipedia so if anyone speaks the below and can translate, that would be awesome-sauce, thank you 🙂  Also, '4.3-6.5 amp drain' -concerns me... can that be the alternator? Or is my car infested with electrical parasites?  Thank you!! (Also, having hunted through a couple of Audi forums about the subject line I've just posted, I apologise if this a subject which has been spoken about repeatedly. I've taken note of replacing the AC sensor and also the air-flow module in the front. Also, about using a voltage meter to check the fuses for draw one by one. But before I start swapping out car parts and potentially causing more issues would just like some guidance 🙂 Cheers     CAN bus - A0P / Gateway 3.2 Status :0B39 - Communication with reversing camera system. Error Message : No signal. Error sporadic. Status :0180 - MOST data bus. Error Message : Open circuit. Error sporadic. Status :0BE1 - Energy management active. Error Message : . Error sporadic. Status :0214 - Power supply. Error Message : Less than minimum. Error sporadic.IV At 11.46v. 4.3-6.5 amp drain. Initial battery test shows battery req charging. Boost stared at boost points. Checked charging at 13.85v 96.5 amps. Battery testing ok needs charging

[Steve Q]

It does sound very strange, the fact the radio turns itself on when car is locked could easily be the cause of this, so the mmi definitely needs looking at thoroughly. I'd recommend an auto electrican to take a look.at the car. If the garage can't diagnose it then they should be sending it to Audi for the repair in my opinion. 

[Beck123]

On 9/6/2022 at 6:22 AM, Steve Q said:

It does sound very strange, the fact the radio turns itself on when car is locked could easily be the cause of this, so the mmi definitely needs looking at thoroughly. I'd recommend an auto electrican to take a look.at the car. If the garage can't diagnose it then they should be sending it to Audi for the repair in my opinion. 

Hi Steve, thank you for the reply…the dealer I bought the car from took it to their local that couldn’t find a fault so it ended up going to Audi. Audi said it was the alternator which I find bizarre. But I’m not knowledgable on these things. When I’ve tried to speak to the dealer he doesn’t seem to have any in-depth awareness of what the issue is. He’s just said that they had to send it to an Audi specialist in the end and they said the alternator was faulty. So they are replacing it. I’ll have to Google if an alternator can have an intermittent fault causing auxiliary things to have a drain. Maybe because it’s not charging the battery correctly this could be the case. 
 

Before I took it back on warranty - because the dealer isn’t close to me I had a garage do a VAGCOM and battery test and they said when the car was off there was a drain. Much like the AA report. Seems pretty high to me though for it to be auxiliary things? But maybe that’s combined with the alternator? The garage wasn’t knowledgable on drain issues and they plus AA just said to let the dealer sort it. As you say I’m not confident it is the alternator as I’ve been told. It’s still under warranty for a while but taking the car back and forth is a pain. I’ll take it to an electrician for diagnosis once I get it back for peace of mind. Thank you

[Steve Q]

You're welcome, it's bad when Audi can't get to the bottom of it.