Engine light after topping up Adblue

[Leesmith1989]

Hi,

Post virgin.

I brought a 2016 C Class Friday and I got home and went to top up any fluids that needed doing.

I noticed the adblue had about 1/3 of a tank so I added 4L. Since then it now tells me it can't determine the level and an engine light has come on. I have no adblue warning whatsoever. It measured the adblue fine until I topped it up the 4L.

Is adding 4L wrong? Should I be adding enough to fill it up? Or is there something else at play here. If so, I'll take to a local specialist to have a look at it.

Thanks

 

[OneForTheRoad]

It'll want adapting to read the new values . Hopefully that will work , otherwise you best keep £1200 to one side

Or have it deleted from the ECU , but then the cars illegal to be on the roads ,officer .

 

[markjay]

If the AdBlue sensor in the tank failed, then a new tank will be required (unless you can get hold of a second hand tank on eBay and move the sensor), and the cost will be as OneForTheRoad suggested.

For this reason, if you bought the car from a dealer or a trader, then I suggest that you take it right back to them asap and get them to sort it out under warranty.

If you bought the car privately, then your best option is to take it to a reputable independent specialist (and not to a dealer).

 

[OneForTheRoad]

Also try adding a bottle of forte anti crystal, it may de scale the sensors inside the ad blu tank.

It's bought btw . Not brought. Pet hate of mine

 

[Slartibartfast]

Also try adding a bottle of forte anti crystal, it may de scale the sensors inside the ad blu tank.

It's bought btw . Not brought. Pet hate of mine

It's "AdBlue or Ad Blue or Ad blue" btw

Just jesting with you

 

[OneForTheRoad]

It's "AdBlue or Ad Blue or Ad blue" btw

Just jesting with you

Ha ha . Gotcha . I'm gonna start calling it DEF from now on.

 

[markjay]

It's "AdBlue or Ad Blue or Ad blue" btw

"btw"? See below:

 

[Slartibartfast]

"btw"? See below:

Well spotted

 

[W1ghty]

You have MBS , a Merc independent specialist in Southampton .
Even if you bought the car privately, a diagnostic scan may show when this fault first developed and was sold to you with this expensive (?) fault . Even a private seller is on the hook for this .

 

[Leesmith1989]

Thanks all.

It was sold via a dealer albeit up north. They have asked for me to see a local garage sgr so I'll make some calls to MDS.

 

[W1ghty]

Thanks all.

It was sold via a dealer albeit up north. They have asked for me to see a local garage sgr so I'll make some calls to MDS.

https://r.search.yahoo.com/_ylt=Awr.htYhT9ZjsBEpV.oM34lQ;_ylu=Y29sbwNpcjIEcG9zAzEEdnRpZAMEc2VjA3Ny/RV=2/RE=1675018146/RO=10/RU=https%3a%2f%2fwww.mbssouthampton.co.uk%2f/RK=2/RS=eBhqKQ952WlAGJUBc8g1q63slj8-

 

[grober]

You may have overfilled the tank -- its gets its level from waves reflected from the liquid surface to the sensor in the bottom of the tank IF THERES NO LIQUID "SURFACE" then it cant get a MEANINGFUL READING---TRY SYPHONING OUT A LITRE OF ADBLUE TO SEE IF THAT CURES THE PROBLEM?

 

[Leesmith1989]

You may have overfilled the tank -- its gets its level from waves reflected from the liquid surface to the sensor in the bottom of the tank IF THERES NO LIQUID "SURFACE" then it cant get a MEANINGFUL READING---TRY SYPHONING OUT A LITRE OF ADBLUE TO SEE IF THAT CURES THE PROBLEM?

How do you get it out? I'm not aware where the tank is

 

[markjay]

You may have overfilled the tank -- its gets its level from waves reflected from the liquid surface to the sensor in the bottom of the tank IF THERES NO LIQUID "SURFACE" then it cant get a MEANINGFUL READING---TRY SYPHONING OUT A LITRE OF ADBLUE TO SEE IF THAT CURES THE PROBLEM?

Google search seems to support this:

"...The client had already told us that he had overfilled the system, which shouldn’t happen when working with an ultrasonic sensor system. Fortunately, our knowledge and experience have taught us that if you overfill the AdBlue system, the ultrasonic sensor is unable to detect the level and thus misleads the vehicle’s electronics.

After draining the AdBlue tank system, we refilled the tank to the correct level. Once the Mercedes C220’s AdBlue level was correct, we took it for a test drive to confirm that the Engine Management Warning light had disappeared and it was back to being reliable and road safe."

From:

https://donnellanauto.ie/2022/06/06/mercedes-benz-c220-adblue-system-failure-error-code-p120300-fixed/

 

[OneForTheRoad]

How do you get it out? I'm not aware where the tank is

I've added 10 litres to a half full tank and not had an issue . My guess is crystals on the sensors.

 

[markjay]

Also, the AdBlue system on Mercedes Benz cars has the potential of becoming problematic, and it is very costly to repair when it does go wrong. If you own a car that is equipped with the AdBlue system, my advice would be to ensure that the car is covered throughout your ownership by a mechanical breakdown warranty that also covers the AdBlue tank, sensors, pump, and injectors, the DPF and its sensor, and the NOx sensors. The trader who you bought the car from should provide some warranty under the Consumer Rights Act 2015, but the seller's liability is reduced over time (30 days / 6 months / 12 months).

PS - this is a general advice, i.e. I do appreciate that there may be nothing currently wrong with the AdBlue system on your car, and that draining it or cleaning the sensor etc might resolve the current issue.

 

[DSM10000]

You have MBS , a Merc independent specialist in Southampton .
Even if you bought the car privately, a diagnostic scan may show when this fault first developed and was sold to you with this expensive (?) fault . Even a private seller is on the hook for this .

Only if they knew about the fault and failed to declare it. As no fault was displayed at point of sale they could reasonably say that they were unaware.

 

[markjay]

Only if they knew about the fault and failed to declare it. As no fault was displayed at point of sale they could reasonably say that they were unaware.

True.

 

[W1ghty]

Only if they knew about the fault and failed to declare it. As no fault was displayed at point of sale they could reasonably say that they were unaware.

Does not being ”aware” of a fault protect a private seller from any comeback though ? If it does I’ll get Mrs W to sell my cars

 

[DSM10000]

Does not being ”aware” of a fault protect a private seller from any comeback though ? If it does I’ll get Mrs W to sell my cars

As long as you do not misrepresent a car when selling privately.

If you knew it had faults that affected drivabiliyy or road worthyness then you, as a private seller could be held liable.