SEAN MG

Hi Steve, thanks for this info, yes my mechanic ran diagnostics on the car and cleared all errors after I changed the battery and coded it. I haven't seen the battery voltage drop below 11.9V but I am keeping it topped up either by driving it or with the charger when parked. What would you expect a standard A4 battery voltage to drop to if parked, for say, 3 days? I will the battery voltage level over a 3 day period while parked. It could be that coding the battery has solved my issue. However, the timing belt, water pump and EGR cooler and associated parts were changed earlier in the year. I see references online where similar changes triggered issues with the adblu control unit (see https://forums.ross-tech.com/index.php?threads/31188/). This may not be the issue in my case. I will hold off on changing out the control unit, this could just be the main dealer trying to cash in on my misfortune! The dealer insisted that the adblu control unit was the source of my problems

Hi Steve, that is very interesting. The original battery, that came with the car suddenly drained (suspiciously a week after a Start/Stop system fault error appeared). I just thought this battery was at end of life after ~8 years. I jumped the car and went to a garage and had a Monbat 12V AGM fitted (but not coded). You are most likely correct on the brand and lack of coding here causing an issue. This battery was completely dead after the 2 week timeframe parked up. A battery shouldn't drain this fast! The car was dead so I had to replace the battery myself with a Ducellier 12V AGM. I got my mechanic to clear errors caused by disconnecting the battery and to code it in. When I keep driving the car daily I have no issues. Battery stays between 12V and 12.7V. When I'm not driving for a few days I am topping up with a trickle charger. This is not a solution long term so looking to change the adblu control unit to resolve the issue (if what the main dealers mechanic tells me is correct!). Your point though is interesting though. You said the power spike is a mechanism of self diagnostic for the car. If this spike is always there how does it not drain the battery if it is parked for a period of time? Do you know what voltage level the battery voltage can drop to before the battery is permanently damaged? Thanks

Hi All, I have experienced battery drain issues in my Audi A4 B9 2016 110W 2L diesel. A new battery was drained in 2 weeks (car was parked up while on holidays). Investigation (ammeter in series with the battery) showed an intermittent current spike 0A to ~0.5A with the car turned off and boot lock closed so car should be in full power down. I couldn't find the source of the issue so dropped it into Audi main dealers. They identified the issue source as the adblu control unit not powering down. The cost for main dealer to supply and fit the unit to resolve the issue is 1.5k euro! I walked away and looking to source the part online and get it fitted and coded in by my local mechanic. Part# is 4M0907355B. From the info online this part looks like it is used in 2015 - 2019 A4 B9 models. It also looks like the engine capacity (2000 to 2993 cm3) doesn't require a different part. Anyone out there changed one of these and can confirm that the 4M0907355B adblu control unit from any 2015 - 2019 A4 B9 model or engine capacity can be coded to my car? Thanks