16074-ZY3-000 Honda O-RING (Honda Code 6989883).

Illustration 1 g06411335
Typical example
(1) Exhaust inlet
(2) Diesel Particulate Filter (DPF)
(3) Selective Catalytic Reduction (SCR) system
(4) Exhaust out
(5) Nitrogen Oxide (NOx) sensor
(6) Diesel Exhaust Fluid (DEF) injector
(7) Diesel Exhaust Fluid (DEF) supply line
(8) Coolant return to engine line
(9) Diesel Exhaust Fluid (DEF) pump
(10) Coolant supply from engine line
(11) Coolant diverter valve
(12) Diesel Exhaust Fluid (DEF) tank
(13) Suction connector
(14) Coolant supply connector
(15) Backflow connector
(16) Coolant return connector
(17) DEF suction line
(18) DEF backflow line
(19) Electronic Control Module (ECM)The Diesel Exhaust Fluid (DEF) Dosing Control System consists of the following components.
DEF pump
DEF injector
DEF header
Coolant diverter valve
DEF system heated linesDiesel Exhaust Fluid (DEF) Pump
Illustration 2 g06300396
Typical example
(1) Inlet
(2) Backflow
(3) Outlet
(4) DEF filter
(5) Electrical connectionThe pump supplies filtered DEF fluid to the DEF injector. The pump consists of inlet port (3) which is the suction side of the pump. The pump then pressurizes the fluid up to 900 kPa (131 psi) and supplies the fluid though outlet port (3). There is a fixed orifice within the pump that purges the pressure off the pressurized circuit. This pressure relief will stabilize the pressure in the line when the DEF injector is opening and closing.Once the engine is shut down, the pump will start to go into a purge mode. The DEF Injector will open and the reverting valve within the pump will reverse the flow of the pump and purge the pump and pressure line. This reversed flow will route any remaining DEF fluid back to the tank.Refer to Operation and Maintenance Manual for the correct procedure to replace the DEF filter.Electric Components of the DEF System
The electric components of the DEF system consist of the following components:Coolant Diverter ValveControls coolant flow to the DEF tank and pump.Heated LinesThe heated lines are electrically heated lines that will turn on any time the ambient temperature is cold. These lines will thaw frozen DEF after starting in cold ambient temperatures. The heated lines will also stay heated during operation to prevent any freezing during operation.DEF Level SensorThe level sensor will measure the amount of DEF in the tank. The system uses an ultrasonic level sensor to determine the amount of DEF in the DEF tank. To measure the level of DEF, the sensor measures the distance to the surface of the fluid. The sensor provides a signal to the ECM that will be converted into a "DEF Level Percentage".DEF Tank Temperature SensorThis sensor is at the bottom of the tank and is integrated within the DEF Level Sensor.DEF Quality SensorAt the bottom of the tank header next to the DEF tank header filter is the DEF quality sensor. The ultrasonic DEF quality sensor uses the speed of sound within a fluid to identify the concentration of the fluid. This is achieved by measuring the time taken for the emitted ultrasonic signal to be reflected off a known fixed reference point. Based on these chemical properties and fluid temperature, the sensor is able to detect urea concentration with an accuracy of up to 2 percent. If the sensor detects the quality of DEF is not within specifications, a fault code will trip indicating the DEF concentration is not correct. The engine may derate.DEF Tank
The DEF tank stores the DEF. The size of the DEF tank will depend on the application.The DEF solution is made of 32.5 percent urea solution and 67.5 percent deionized water. Urea is a compound of nitrogen that turns to ammonia when heated.Ensure that the correct specification of DEF is used. Refer to Operation and Maintenance Manual for more information.DEF does degrade over time at elevated temperatures. Due to freezing risk, the tank, pump, and lines must be heated and designed to contain frozen DEF.DEF Tank Header
Illustration 3 g06357840
Typical example
(1) Coolant tubes
(2) DEF pickup tube
(3) DEF tank header filter
(4) DEF tank temperature sensor, level sensor, and quality sensorThe DEF tank header is located in the DEF tank. The tank header consists of several parts and performs the following functions:Coolant TubesThe coolant supplied by the engine will flow through the tubes when the coolant diverter valve opens. Coolant runs along the pickup tube to the bottom of the tank and then spirals around the level sensor. The heat from the coolant will thaw any frozen DEF in the tank or header. The heat will also prevent the DEF from freezing around the pickup tube.DEF Pickup TubeThe DEF is pulled from the bottom of the tank through a screen.DEF Tank Header FilterAt the end of the DEF Pickup tube is a 40 micron filter to filter debris from entering the system.DEF ReturnThe DEF is returned back to the tank from the DEF pump.DEF Tank Temperature SensorAt the bottom of the tank header near the DEF tank header filter is a tank temperature sensor. The temperature sensor is a passive thermistor. The resistance of the thermistor varies with temperature. This sensor monitors the temperature of the DEF in the tank. This temperature is used to determine when to turn on the coolant diverter valve.Coolant Diverter Valve
Illustration 4 g03403819
Typical example
(1) Flow direction indicatorThe coolant