Search for an Audi A4 B9 2.0 TDI review and Google will soon suggest "AdBlue problem". Coincidence? I don't think so. The Audi A4 B9 (8W), built from 2015 to 2023, is an excellent car. It's comfortable, has an economical diesel engine and enough technology to still feel modern today. But there's one system you really need to know about before spending your money. It's called AdBlue, and it can turn an otherwise great purchase into a nasty surprise.
Who is the Audi A4 B9 2.0 TDI right for?
If you cover a lot of miles and want a comfortable car that's economical to run, the A4 B9 2.0 TDI is definitely worth considering. This is a car built for long journeys, not just to look good parked outside your home. You get modern equipment, good driver assistance systems and a more premium feel. But all those features mean more electronics, and they need proper diagnostics and maintenance. That's why I don't just look at how a car drives. I also check what's happening inside its systems.
What engines and gearboxes does the Audi A4 B9 have?
The diesel A4 B9 uses the 2.0 TDI engine from the EA288 family. It comes in several versions, and the names changed after the facelift. Don't get confused by the badges on the boot. What matters more is the exact version you're buying and whether it's been properly maintained.
- 2.0 TDI EA288 – 150 and 190 hp versions, the main options in this range.
- After the facelift – the names changed to 35 TDI and 40 TDI.
- Gearboxes – 6-speed manual or 7-speed S tronic automatic.
- Drive – quattro versions are available, some using the quattro ultra system.
I wouldn't choose a car just because of its power output or whether it has quattro. The condition of the actual car, its service history and the diagnostic results matter far more. A well-maintained car is a much better buy than one with impressive equipment but an unknown past.
Audi A4 B9 2.0 TDI review: What problems should you expect?
Now we get to the most important part of my Audi A4 B9 2.0 TDI review. At Das Auto Service, we pay particular attention to a few systems because they're the ones that can make a big difference to what you spend after buying the car. That doesn't mean every car will have these problems. It means you need to know where to look.
AdBlue – why does the "no engine start" warning appear?
AdBlue is the first system I'd check. Problems can come from the heater and pump inside the tank, the NOx sensors or the AdBlue dosing injector. When the system detects a fault, the dashboard may show a countdown of the kilometres remaining before the engine can no longer be started. And this isn't just an annoying warning you can ignore. I've explained it in detail in AdBlue problems on the 2.0 TDI EA288.
EGR cooler and DPF – what should you watch for?
If the coolant level keeps dropping but you can't see a leak anywhere, the EGR cooler needs checking. Simply topping it up and carrying on driving isn't enough. The other system I pay attention to is the DPF, or diesel particulate filter. If the car is mainly used for short journeys around town, the filter can become clogged and cause further problems. That's why it matters how the previous owner used the car.
S tronic – why does the gearbox jerk or hesitate?
If the gearbox jerks or snatches when you pull away, don't automatically assume that's normal for an S tronic. The mechatronic unit, which controls the gearbox, and the condition of the oil need checking. For me, the service history is an essential part of assessing a car like this. The gearbox oil must be changed every 60,000 km using genuine oil, and we always carry out an adaptation afterwards. Simply filling the gearbox with fresh oil doesn't complete the job.
Electronics – when is calibration needed?
The Audi A4 B9 has plenty of electronics, so don't underestimate the importance of proper diagnostics. The MMI software and driver assistance systems also deserve attention. It's especially important to find out what work has been done after a windscreen replacement or an accident. In these cases, the camera and radar need the appropriate calibration. Just because everything looks fine doesn't mean it is.
What should I check before buying an Audi A4 B9?
When buying a used A4 B9, I'd start with a diagnostic check, not a quick acceleration test. The car might drive beautifully and still have a problem you can't yet feel behind the wheel. Here's the order I'd recommend.
- Full diagnostics of the AdBlue system, NOx sensors, EGR and DPF.
- Check the coolant level and find out why it's dropping if there's any coolant loss.
- Check the S tronic service history and how the gearbox behaves.
- Check the car's service history and actual mileage.
All of this is included in our pre-purchase inspection. The idea is simple: know exactly what you're buying before you hand over your money. A beautiful interior and plenty of equipment are no substitute for a proper mechanical inspection.
How should I service an Audi A4 B9 2.0 TDI?
Proper servicing starts with consistency. I don't wait for a car to develop a problem before giving it attention. For cars driven in Bulgaria, we follow specific service intervals at Das Auto Service, regardless of what the LongLife programme allows.
- Engine oil and filters – every 10,000 km or once a year, whichever comes first, regardless of the oil used or the LongLife programme.
- S tronic – change the gearbox oil every 60,000 km, always using genuine oil, followed by the required adaptation.
- AdBlue – use only fluid that meets ISO 22241, from a sealed container.
- Brake fluid – change every 2 years.
- Coolant – change every third heating season.
- Preventative workshop inspection – every 6 months.
You can find the full schedule here: Audi A4 B9 2.0 TDI service schedule. I prefer regular, planned servicing to repairing a car after a serious problem develops. That way, you know exactly what's been done and what's coming up next.
WARNING! If an AdBlue fault appears and the dashboard starts counting down the remaining kilometres, don't wait until it reaches zero. Once it does, the car may simply refuse to start.
Is the Audi A4 B9 2.0 TDI worth buying?
Yes, definitely. For me, the Audi A4 B9 2.0 TDI is one of the best cars in its class when it comes to comfort, fuel economy and covering long distances. But I wouldn't buy one without checking the AdBlue system and gearbox first. If both are in good condition, the servicing is documented and the diagnostic check doesn't reveal anything worrying, you've got every reason to consider it an excellent choice. That's my verdict.
Tip from Kris Mladenov: On an Audi A4 B9, check the AdBlue system with a diagnostic tool first. Don't just rely on the absence of dashboard warnings. Then pay attention to the S tronic gearbox and the service history. These checks can make the difference between buying with confidence and getting a nasty surprise a month later.
I hope you've found this article useful! If you have, I'd be happy if you shared it with a friend who owns or is thinking about buying an Audi A4 B9 2.0 TDI. My mission is simple: when I know something, I want more people to know it too. Because an informed owner makes better decisions about their car.
The solution in our shop
Genuine Longlife III FE 0W30 oil 5L
LongLife III engine oil for engine servicing. Regardless of the LongLife specification, stick to the 10,000 km or 1-year service interval.
View in shop
Genuine VAG AdBlue® fluid G052910M4 10l
Genuine AdBlue in a 10-litre container for the exhaust emissions treatment system. Use fluid that meets ISO 22241.
View in shop
Genuine Audi/Volkswagen DOT 4 brake fluid B000750M3 1l
Genuine DOT 4 brake fluid for brake system servicing. Change every 2 years.
View in shopRead more
- Pre-purchase inspection
- Diagnostics
- Audi A4 B9 2.0 TDI service schedule
- AdBlue No Start in 1000 km: 2.0 TDI EA288
Frequently asked questions
What is the AdBlue problem on the Audi A4 B9?
The main things to check are the heater and pump inside the tank, the NOx sensors and the AdBlue dosing injector. If a fault develops, the car may start a countdown until the engine can no longer be started.
Should I choose the 150 or 190 hp Audi A4 B9 2.0 TDI?
I'd choose based on the car's mechanical condition and service history, not just its power output. Both versions belong to the EA288 engine family.
When should the S tronic oil be changed on an Audi A4 B9?
At Das Auto Service, we change the gearbox oil every 60,000 km using genuine oil. We always carry out an adaptation after servicing.
Is a used Audi A4 B9 2.0 TDI worth buying?
Yes, provided the AdBlue system has been checked, the gearbox has been properly serviced and the car has a clear service history. I strongly recommend a full diagnostic check before buying.