Your MBZ is a non-EGR valve equipped vehicle; which means all the NOx control is on the fuel control system and the CAT. If the air/fuel mixture is lean, it will cause high NOx... also if the Catalytic Converter is defective it will cause high NOx. We recommend first ensuring your Mercedes is not runnning lean (lack of fuel to the cylinders), and next inspect the CAT for proper operation.
posted by SmogTips Support
