2013 A4. New Alt, new Battery.

[Buffmaloney]

Won't start after sitting for over 24 hours. I got codes. Had the battery and alternator checked. The voltage regulator was bad. New alternator. Still got codes and car won't start. Battery checked. Bad cell. New battery. Let car sit for over 24 hours to see if it was fixed. Still won't start. From the beginning I could clear all codes but one and the car would start. One kept coming back after cleared.

U0100 Code​

After the new alternator was installed, when the car sat for 24 hours or more, it would not start even after clearing codes. On a whim I tried to jump the car. It started right up. That is when I had the battery checked and got a new battery. It was installed at 10AM yesterday. Today at 1PM it will not start. I am going out to check if there are codes and if it will start when jumped. Any ideas?

 

[NHN]

Thats a code for loss of comms with a module, however...,

Battery may have been ok all along & something's flattening them.

Do you have any aftermarket devices on the car?

 

[Buffmaloney]

Thats a code for loss of comms with a module, however...,

Battery may have been ok all along & something's flattening them.

Do you have any aftermarket devices on the car?

No. All stock. There is a dashcam that is always hooked up. But this is the 3rd car it has been in and has never caused any issues.

 

[ninjag]

No. All stock. There is a dashcam that is always hooked up. But this is the 3rd car it has been in and has never caused any issues.

Could be worth double checking the dashcam, maybe have a look at the current draw and voltage drop? My dashcam battery protect appears to have failed in some way at the weekend and kept my camera running 24/7 which hurt my battery.

Another thought could be that sometimes new batteries aren't fully charged? I also bench charge a new battery to full before installing - could be worth checking that as well?

 

[pelhamsdetailing]

No. All stock. There is a dashcam that is always hooked up. But this is the 3rd car it has been in and has never caused any issues.

Live or ignition-live? If it's the former, then that's likely causing a constant drain.

 

[Buffmaloney]

Live or ignition-live? If it's the former, then that's likely causing a constant drain.

Ignition. It may come on if it detects movement, but that might be the dashcam in the other car.

 

[Buffmaloney]

Local mechanic said that with it having a U code that I probably have to take it to Audi and get my butt reemed. They do not have the equipment for that car. Probably has a password to get in and fix. Where is the CAN module? Correct my logic if needed. Battery new, won't start. Will start when jumped by hooking up to the spots under the hood. Therefore something is bad between the battery in the trunk and the ECM.

 

[ninjag]

This might be a Hail Mary, but may as well throw it out there. When I was looking up solutions for my own recent problem I came across a few posts about water ingress through the scuttle panel and onto the ECU box/area. Could be worth a look just to rule that out?

 

[samhoward95]

Recently went through this on my Mondeo. You have a new alternator and battery, doesn't seem logical for it to work when jumpstarting it if there was a fault.

Have you tried taking it for a long drive to charge up, then come home and check battery voltage while still running? Then switch off, check again. Then lock car, go watch some TV then go and check an hour later, see if it's dropped much.

Process of elimination, but once I had solved the issue on my Mondeo (faulty door lock, and dead battery even though it was only a year old) it starts first time now

 

[Buffmaloney]

Recently went through this on my Mondeo. You have a new alternator and battery, doesn't seem logical for it to work when jumpstarting it if there was a fault.

Have you tried taking it for a long drive to charge up, then come home and check battery voltage while still running? Then switch off, check again. Then lock car, go watch some TV then go and check an hour later, see if it's dropped much.

Process of elimination, but once I had solved the issue on my Mondeo (faulty door lock, and dead battery even though it was only a year old) it starts first time now

I have not dared go on a long drive. Haven't had the time yet either. I assume you know that the battery for this car is in the trunk, under the spare tire and you jump it off under the hood.

 

[Buffmaloney]

Here are the latest codes, including the U0100 code,

CAN Network gateway 01314
Ignition Authorization 00956, 01330
Instrument cluster 01314
Parking brake 334080, 331264, 331520, 460800
Engine 04533, 10577
Transmission 12551, 12554, 12562
Power steering 3158274

 

[Buffmaloney]

A big thanks to everyone that helped. I think the car is finally fixed.

 

[pelhamsdetailing]

Well done mate - it would be worth posting the fix for your issue so that others with the same issue who find this thread can potentially apply the same fix.

 

[Buffmaloney]

https://static.nhtsa.gov/odi/tsbs/2014/SB-10055713-5611.pdf