how many times do you know of that 'bad def' was actually to blame?DEF has a limited shelf life and it's dependent on stowage temperature. I only had to buy one container so far and was not happy that there was no data for expiration nor manufacture date on the package. Given the potential expensive repairs possible, maybe the cheapest way to try and fix this is to extract the DEF and fill with fresh fluid? Hope it's not any worse than that. Do keep us posted on how you correct this problem.
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im not aware of any.
neither are the 20 or field mechanics that ive asked.
100+ yrs of experience, and no time was the def ever 'bad'