Initial Check

WARNING: This page is about a different car, the 2018 Nissan Titan XD. However, it is still accessible from the selected car via links, so may be relevant.

Check for any leaks, blockages, or restrictions in the DEF line between the after treatment DEF dosing unit and the after treatment DEF dosing valve.
Check for an adequate amount of DEF in the DEF tank prior to starting this test.
Check the concentration and quality of the DEF.