AdBlue reading stuck on 100%

[steve101]

My CX5 adblue reading on the dash has been stuck on 100% since the secong service in September 2020. The car had done just over 5,000 miles between services so the adblue should have been showing around 50%. At the third service in August this year the mechanic said it didn't need topping up and just to keep an eye on it. I have contacted Mazda customer service and told them about this issue. They have recommended that I run the car for another 3,000 to 5,000 miles and if it is still stuck on 100% to get it checked out at the nearest dealer.
Has anyone else had this issue?

[BigAl]

No, but for what it's worth, my 2018 had only used about 70% of the adblu by first service at 12,500. It was nearer 14k when I eventually filled it. Note that refilling this is not a standard part of the Mazda 12.5k service, although some dealers will do it, usually at drivers request.

[bw10030]

Any update on this? My 2022 model is doing exactly the same.

[bw10030]

Well mine has been stuck on 100% for about a year, however the mileage has been decreasing. I filled the tank up at a Adblue pump and probably overfilled it - I got warnings for a couple of weeks afterwards! The mileage has now come down by 10000 miles (yes really! - ten thousand) and today it finally showed 95% full.

So it looks like if you overfill, it goes to something like 200% measured capacity (must be a long filler neck!) but it will decrease and start working again eventually.

I mentioned it at the dealers - Mazda are aware and will drain the tank (for a charge) to get it working again. Leave well alone if it costs is my advice!

My next plan is to wait until it shows about 50% and then put 5 litres in, then see what it goes to. That way I can be confident its working OK. If the mileage readout was to be believed, I had enough Adblue for 26000 miles when it was full!

It's poor design - either you should not be able to overfill, or if you do then after a short distance (say 500 mies) it should start to work again. This looks like there is an awful lot of the tank above the 100% full (according to the gauge) which you have to use before it starts to read again, which isn't a good plan!