KEY 9D2717 - Caterpillar

Illustration 1 g03432366
Typical example
(1) Exhaust inlet from back pressure valve
(2) Selective Catalytic Reduction (SCR) system
(3) Exhaust out
(4) Nitrogen Oxide (NOx) sensor
(5) Diesel Exhaust Fluid (DEF) injector
(6) Diesel Particulate Filter (DPF)
(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) Coolant supply connector
(14) Suction connector
(15) Backflow connector
(16) Coolant return connector
(17) DEF suction line
(18) DEF backflow line
(19) Dosing Control Unit (DCU)
(20) Electronic Control Module (ECM)
Illustration 2 g03432395
Typical example
(21) Pump Electronics Tank Unit (PETU)
(22) Diesel Exhaust Fluid (DEF) tank filler cap
(10) Coolant supply from engine line
(8) Coolant return to engine line
(19) Dosing Control Module (DCU)
(12) DEF Tank
(7) Heated DEF line
(23) Harness connections
(24) DEF drain plugThe Diesel Exhaust Fluid (DEF) Dosing Control System consists of the following components.
Pump Electronics Tank Unit (PETU)
DEF injector
DEF System Heated LinesPump Electronics Tank Unit (PETU)
The Pump Electronics Tank Unit (PETU) consists of the following components.
DEF tank
DEF pump
DEF header
Coolant diverter valve
Dosing Control Unit (DCU)The Dosing Control Unit (DCU) is mounted on the DEF pump assembly.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 Pump
Illustration 3 g03403876
Typical example
(1) Inlet
(2) Coolant inlet
(3) Backflow
(4) Coolant outlet
(5) Outlet
(6) DEF filterThe pump supplies filtered DEF fluid to the DEF injector. The pump consists of inlet port (1) which is the suction side of the pump. The pump then pressurizes the fluid up to 896 kPa (130 psi) and supplies the fluid though outlet port (5). 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.The DEF inlet and backflow connectors have a 100 micron screen to filter any debris in the system.Engine coolant is routed through the pump to warm the pump during cold-weather operation.Refer to Operation and Maintenance Manual for the correct procedure to replace the DEF filter.DEF Tank Header
Illustration 4 g06132474
Typical example
(1) DEF tank header filter (32 micron) (if equipped)
(2) Coolant tubes
(3) DEF level sensor (float)
(4) DEF pickup tube
(5) DEF tank header filter (100 micron)
(6) DEF tank temperature sensor (integrated within DEF level sensor, not shown)
(7) DEF quality sensor (if equipped)
(8) DEF back flow tubeThe DEF tank header is located