91301-PM5-A01 Honda O-RING (9.8X1.9) (Honda Code 2710820).

Illustration 1 g03842768
(1) Post NOx Sensor
(2) SCR (Selective Catalytic Reduction)
(3) Cooling Water Valve
(4) DEF (Diesel Exhaust Fluid) Pump
(5) Temperature Sensor
(6) ACU (Aftertreatment Electronic Control Unit)
(7) DEF Injector
(8) Mixer Pipe
(9) Pre NOx Sensor
(10) Diesel Particulate Filter (DPF)
(11) DEF Tank
(A) Exhaust Gas Before Purification
(B) Exhaust Gas After Purification
(C) Cooling Water Hose
(D) DEF HoseThe Diesel Exhaust Fluid (DEF) Dosing Control System consists of the following components.
DEF Electronics Unit (PEU)
DEF Tank and DEF Header
Coolant Diverter Valve
DEF System Heated LinesPump Electronics Unit (PEU)
The Pump Electronics Unit (PEU) consists of the following components:
DEF Pump
Dosing Control Unit (DCU)The DCU is mounted on the DEF pump assembly.
Illustration 2 g03842871
(1) DEF Pump
(2) DEF Inlet
(3) DEF Outlet
Illustration 3 g03842894
(4) DEF FilterThe DEF pump (1) supplies filtered DEF fluid to the DEF injector. DEF is fed to the pump (1) from the DEF tank through inlet port (2), which is the suction side of the pump. The DEF is filtered by filter (4). The pump pressurizes the fluid to outlet (3) to the DEF injector. The DEF Pump has an internal electric heater to prevent DEF from freezing and is turned on 2.4 seconds after engine start and will turn off once DEF pressure reaches 350 kPa (51 psi).After engine start, the DEF pump will prime the system which will take between 30-60 seconds. The pump will maintain approximately 350 kPa (51 psi) to circulate DEF through the system, which cools the DEF injector. This prevents the injector from overheating from the hot exhaust gases. During DEF injection the pump will increase pressure to 550 kPa (80 psi).Once the engine is shut down, the DEF pump (1) will continue operation in cool down mode in order to cool the DEF injector. The cool down mode can take up to 10 minutes. The DEF pump (1) will then proceed to a purge mode. The DEF pump (1) will reverse the flow to purge the supply, pressure, and return lines. This will return any DEF back to the tank. The DEF injector will remain closed during the purge mode. The purge process can take up to 2 minutes.Note: If the machine has a battery disconnect switch, ensure the "DEF Purge Indicator Lamp" is OFF before disconnecting the battery. This will ensure the DEF has been purged from the lines and the DEF injector has been cooled. Disconnecting the battery with the "DEF Purge Indicator Lamp" ON may cause failure of the DEF injector due to overheating or the DEF lines from the DEF freezing. Refer to the Operators Maintenance Manual (OMM), "Battery Disconnect Switch" for the proper procedure.The DEF filter (4) has a 3,000 hour service interval. Refer to the OMM for the correct procedure to replace the DEF filter (4).Dosing Control Unit (DCU)
Illustration 4 g03858438The DCU is mounted to the DEF pump. The DCU is an ECM that controls all the electrical components in the DEF system. While an ECM, the dosing control module is referred to as the DCU. The DCU receives signals from the engine ECM via CAN communication.Based on various sensor values, the DCU controls the DEF injector, DEF pump, and coolant valve. After the engine is stopped, the DCU performs a cool down mode and DEF purge process. Refer to "DEF Pump" and "Cold Weather Operation" for more information.DEF Tank
Illustration 5 g03842922
(1) Fill
(2) Vent
(3) DEF Tank
(4) Drain Plug
(5) DEF Tank Header Assembly
(6) Filter for the DEF Pick-up TubeThe DEF tank (3) stores the DEF. Refer to the machines OMM, "Capacity (Refill)" for refill capacities. The DEF tank consists of a header unit (5), fill (1), vent (2), and a drain plug (6).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. Refer to Operation and Maintenance Manual, "Diesel Exhaust Fluid" and the sections related to “Storage” and “Stability”. Due to freezing risk, the tank, pump, and lines must be heated and designed to contain frozen DEF.DEF Tank Header
Illustration 6 g03843030
(1) Filter for DEF Pick-Up Tube
(2) Coolant Inlet and DEF Pick-Up Tube
(3) Header
(4) Coolant Outlet
(5) Sensor Assembly
Illustration 7 g03843049
(A) DEF Lines are heated and insulated
(B) DEF to pump and then to injector
(C) Sensor: level, temp, and urea concentration
(D) Coolant from water valve
(E) DEF Return from injector
(F) Coolant ReturnThe DEFThe DEF tank header consists of the following components.
Coolant Tubes
DEF Pick-Up Tube
DEF Tank Sensor AssemblyThe coolant supplied by the engine will flow through the coolant 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.DEF pick-up tube pulls DEF from the bottom of the tank through a 300 micron screen (1). The DEF pickup tube is shrink wrapped to the coolant tube to improve thawing performance.The DEF tank sensor assembly (5) monitors the DEF level, DEF temperature, and DEF quality. This is the temperature sensor that is used to determine when to turn on the coolant diverter valve. The DEF quality sensor measures the DEF solution and if not the correct mixture or if diluted, a warning code will be created. The level sensor will measure the amount of DEF in the tank. The sensor provides a signal to the DCU that will be converted into a "DEF Level Percentage".