Operation & Maintenance Manual for WP7 Euro Ⅵ Vehicle Diesel Engine 3.19 Abnormal indication of the urea solution level 3.20 Urea-crystal appear at the nozzle position on the exhaust pipe 20 Causes Troubleshooting 1. Liquid lever sensor of urea solution-tank is failure Check and replace Causes Troubleshooting 1. Wrong urea solution nozzle mounting size Check and adjust 2. The nozzle has leaked Check and replace