What does AdBlue system failure mean?

Don’t you hate it when you’re driving along, minding your own business and boom… the AdBlue warning light shows up?

Leave it too long; your car won’t function as it should, if at all. Luckily, Mr P brought his Audi A8 to our Audi specialists at Donnellan Auto Services before the AdBlue warning light turned into something serious. Although the AdBlue warning light is standard with Diesel engines, it’s not always an AdBlue top-up you need. This was the case for Mr P’s Audi A8.

His car showed an error code (P13DF09) which indicated a malfunction of the AdBlue system. It showed no visible damage, and it was clear the AdBlue system needed checking over with a fine toothcomb. AdBlue systems are complex; a whole host of issues could be causing it to show up on Mr P’s dashboard. I can think of 10+ reasons for the warning light making an appearance.   

When it comes to solving the issue, the real skill is applying mechanical and electrical know-how to identify the problem quickly; only then can you fix it. 

Finding The Problem

At Donnellan Auto Services, our expert technicians evaluate every car using our 15 step diagnostic process. We guarantee to find the root cause of any problem quickly, saving you time and money. During the 15 step process, Mr P’s car passed all of the initial AdBlue assessments. But, it wasn’t until the later stages the primary issue was found… a leaking AdBlue injector system.

Bingo! Now we knew what the leading cause of the problem was.

The system had been leaking for a while and had caused several blockages. It’s no wonder he’d been getting warning lights and error codes. On top of the leaking system and blockages, secondary issues begin to pile up. Poor pressure, irregular spray pattern, and low-quality injection, to name a few.

You can see why it’s critical to find the faults early on. A tiny warning light can quickly become more severe and costly if left unchecked. Before coming to us, Mr P had been to another garage that failed to spot the leaking system. Rather than returning to the garage, he decided to visit us instead.

Our specialists are trained to look beyond the surface issues to find what’s going on. Warning lights have several meanings, which aren’t always clear during a brief assessment. A misdiagnosis is easy to make if you don’t have the right processes.

Sure, topping up Mr P’s car with AdBlue might clear the warning code, but it would come back at some point. The last thing you want to do is mask the problem, as it leaves you having to pay for another garage to look at your car.

Donnellan Auto Services are a big believer in getting you back on the road as quickly as possible without sacrificing quality. We want you to be confident driving out of the garage, knowing your car is safe to drive. 

Solving The Issue

Our Audi technician was sure replacing the leaking injector system would solve the P13DF09 error code.

Once the injector was replaced and sealed only using Audi parts, his AdBlue system ran like new. No warning lights, improved pressure, and a high-quality injection—everything you’d want to see from your AdBlue system.

Audis are well-made cars, so it’s crucial you use the quality parts suitable for the engine. It’s no good using cheap knock-offs; they won’t last long. Unfortunately, some garages buy cheaper parts. But you know how the saying goes, “buy cheap, buy twice”. It costs you more in the long run. We only use genuine Audi or high-quality parts when it comes to fixing your car. Like our technicians, we believe in quality.

After retesting the car, it passed our assessments with flying colours.

Mr P was chuffed to have his car back in working order. He loved that Donnellan Auto Services had taken less than 24 hours to assess, identify, and fix any issues his Audi A8 had. Nothing is worse than having your car sit in a garage for days. This is why we give every client a first-time diagnosis and fix, having you back on the road the same day.

Don’t become a victim of a misdiagnosed fault; it costs you a fortune. Not to forget the time you spend heading back and forth between garages.

Summary

Mr P’s Audi A8’s AdBlue malfunction could have led to a major issue if it wasn’t solved quickly.

Luckily, our Audi specialists at Donnellan Auto Services found the primary issue, fixed the system, and had Mr P back on the road within 24 hours. 

If you’re having issues with your Audi, please call Donnellan Auto Services and speak to one of our experts. Our team are more than happy to help. Call us on 091 792474 and book your car for a premium service without the premium price tag.

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AdBlue is just another name for Diesel Exhaust Fluid or DEF. This solution of urea in water is injected into exhaust gases as a part of the exhaust treatment system called selective catalytic reduction or SCR.

This process converts up to 90% of the harmful nitrogen oxides produced by the vehicle into nitrogen and water. Modern diesel-powered cars combine this with other emission control systems to meet the highest emission standards while retaining high engine power outputs and fuel economy.

How does it work?

AdBlue is stored in an external tank, which has an internal delivery pump. From there, it is injected into the stream of exhaust gases through the injection valve. As AdBlue would freeze in low outside temperatures, the heater element is installed into the tank to prevent this.

Activation and AdBlue dosing is controlled by Electronic Diesel Control unit or EDC. This regulation is based on several parameters:

• exhaust temperature,
• NOx content before and after SCR catalytic converter
• the operational readiness of the AdBlue system itself.

Be aware that AdBlue system in your Mercedes will start working only when all the parameters are fulfilled.

Common faults

• in-tank heater element, which burns out. The only solution is replacing it with a new one.
• injector and connecting tubing clogged up. As this system works only at high exhaust temperatures, urea solution can crystallize if you have frequent short journeys.
• NOx sensor can break or give false readings

Countdown warning system

If there is a problem with AdBlue system, your Mercedes will be limited to a number of starts or miles driven before it is not possible to restart it.

It is very important to deal with any issues regarding the AdBlue system without delay.

Depending on the model, you will get some of the following messages:

• AdBlue Check Additive See Operator’s Manual
• AdBlue Range
• Engine Start Not Permitted (AdBlue Empty)
• Check AdBlue No engine Start Possible in XXX miles/km.
• Check AdBlue Remaining starts: X

While there are ways to reset Mercedes limited start condition (eBay link), it is important to find the root of the problem and fix an AdBlue system that is not working. The two most common AdBlue problems are:

1. DEF fluid low level
2. Fault with the SCR system.

No matter the cause, an AdBlue system that doesn’t work will not have any effect on the engine operation or performance. You can easily drive for years without AdBlue, without affecting your engine. That only works on theory though, because a 2010 and newer Mercedes BlueTec will more likely go into limp mode to prevent you from driving.

2009 and older Mercedes-Benz BlueTec vehicles and Sprinter vans can go over 300,000 miles on the original engine. These cars didn’t have the AdBlue system.

So, why do you get various warnings if the AdBlue system is not working? Well, the answer for this is a very simple one – that is the only thing that will prevent you from driving your Mercedes like that. If there was a warning system such as this countdown, most car owners would not top up DEF when it runs out. And this would increase emissions and pollution.

Troubleshooting

First of all, check the AdBlue level and top it up if needed. You can buy AdBlue fluid from any Mercedes dealer, or you can get a generic Diesel Exhaust Fluid from auto part stores or gas stations.

If there is a fault within the system, the following should be checked:

• Values from temperature sensor upstream of SCR catalytic converter
• Values from NOx sensor control unit upstream of SCR catalytic converter
• Values from NOx sensor control unit downstream of SCR catalytic converter
• AdBlue tank for DEF quality and quantity
• AdBlue delivery pump and injection valve
• AdBlue metering amount
• Visually check for leaks

How do I refill AdBlue?

Make sure to add AdBlue to the correct tank. Do not mix AdBlue with diesel fluid. AdBlue is not an additive or a lubricant. Do not mix water with AdBlue.