Selective catalytic reduction (SCR) is a promising technology for diesel after treatment. SCR can be used to meet Euro IV and even stringent emission standards. Dosing of urea must be controlled to lower NOx emission and NH3 slip simultaneously. An Aqueous solution of urea (AUS 32, Ad Blue and DEF) is used to full fill this requirement. As per the legislation limit (On board diagnostic requirement) the concentration of urea in solution should be 32.5 %. In this paper we discussed about the installation of urea quality sensor and it's on vehicle validation.