31247-ZW1-004 Honda GEAR ASSY. (INNER) (Honda Code 4914719).

Illustration 1 g06471531Reference: For more information, refer to supplemental video "3512E Tier 4 Final Engines for 785G Off-Highway Trucks Dosing Control System Operation (System Warmup)" on Caterpillar Channel1.Note: Click or copy the following link into a web browser (a CWS login is required to access Caterpillar Channel1), or scan the following QR code using a QR enabled device.https://channel1.mediaspace.kaltura.com/media/1_2fo968tn
Illustration 2 g06566871Reference: For more information, refer to supplemental video "3512E Tier 4 Final Engines for 785G Off-Highway Trucks Dosing Control System Operation (Modes of Operation)" on Caterpillar Channel1.Note: Click or copy the following link into a web browser (a CWS login is required to access Caterpillar Channel1), or scan the following QR code using a QR enabled device.https://channel1.mediaspace.kaltura.com/media/t/1_2onkwwst
Illustration 3 g06566877General Operation
Table 1
Single Clean Emission Module Aftertreatment System
DEF Pump DEF Injectors DEF Pressure Line Color
1 2, 3 Blue
2 1, 4 Green
Illustration 4 g06169473
The illustration depicts only 1 DEF dosing system. There are 2 DEF dosing systems for this application (both are identical).
(1) Exhaust inlet
(2) Inlet nitrogen oxide (NOx) sensor
(3) Diesel Exhaust Fluid (DEF) injector
(4) Catalyst brick
(5) Outlet NOx sensor
(6) Exhaust out
(7) DEF supply line
(8) Coolant return to engine line
(9) DEF pump
(10) Coolant supply from engine line
(11) Coolant diverter valve
(12) DEF backflow valve
(13) DEF tank
(14) Coolant supply connector
(15) Suction connector
(16) Backflow connector
(17) Coolant return connector
(18) DEF suction line
(19) DEF backflow line
(20) Dosing Control Unit (DCU)
(21) Aftertreatment Electronic Control Module (ECM)The purpose of Diesel Exhaust Fluid (DEF) is to create a reaction across the Selective Catalytic Reduction (SCR) catalysts to reduce nitrogen oxides (NOx).When the engine is keyed on but not running, DEF is not being injected into the system. When the engine is running, the DEF may be too cold or frozen to be injected. When the ambient or tank temperatures are cold enough, the DEF control unit (DCU) opens the coolant diverter valve to allow engine coolant to flow through the DEF tank to warm the system. The DCU also activates the heater circuits in the lines to prevent DEF from freezing in the lines and pump. The time it takes to thaw the system depends on the ambient temperature. Since the system always starts with empty lines, the pump activates to fill the lines with fluid before DEF injection begins.Once the system is thawed and primed, the DEF will be injected into the exhaust system when the exhaust temperatures are warm enough. If the system does not heat up after duration of time, a diagnostic code will become active.Note: Typical usage for DEF is 1-3% of diesel fluid. The DEF tank is sized to be refilled at the same time as the fuel tank.The DEF system has three operation modes:1. DEF Priming ModeSince the system always starts with empty lines, the pump activates to fill the lines with fluid before DEF injection begins. Priming will start when engine speed is at idle, DEF tank temp is greater than −6° C (21.2° F), and SCR inlet temperature is greater than 180° C (356° F). Once the system reads the appropriate pressures, priming is complete.2. DEF Injection ModeOnce the system is primed, the DEF will be injected when SCR inlet temperature is greater than 250° C (482° F). The DEF pump draws DEF from the tank and pressurizes the DEF to 900 kPa (130.5 psi). This pressure is constant throughout the operating cycle. The DEF injectors spray DEF into the exhaust before the SCR catalyst. The DEF injection rate is controlled by changing the duration of the DEF injector on time. The DEF injector is controlled by a PWM signal. If the engine is producing higher NOx, the DEF injector will be open for a longer duration, allowing more DEF into the exhaust stream. To control the pressure to the DEF injector, a percentage of DEF will flow through the backflow line (controlled by the back flow valve) back to the tank.3. DEF Purge ModeWhen certain DEF fault codes become active or the engine is keyed OFF, the DCU enters purge mode. The system is designed to purge all DEF back to the DEF tank to prevent it from freezing in the pump and lines. The DEF injector opens and the DEF Reverting valve in the DEF pump reverses the flow of the DEF. This removes the DEF from the pressure line and pumps it back to tank through the suction line. The purge takes approximately 2 minutes to remove DEF from the lines and pump. It is important NOT to turn off the battery disconnect switch during the purge process. If the purge process does not complete and the temperature of the DEF drops below −11° C (12° F), then the pump and lines are at risk of damage. If the purge process does not complete a diagnostic code will become active.NOx MonitoringThere are four NOx sensors supplied with the engine. Two NOx sensors are installed in the exhaust inlet from the turbocharger (engine out). The other two NOx sensors are installed in the exhaust pipe of the application (CEM out).The amount of DEF needed is based on NOx production. The engine produces NOx as the engine operates at a specific target to meet emission requirements. The engine out NOx sensors measure the amount of NOx in the exhaust stream at the inlet to the CEM. The tailpipe out NOx sensors monitor the NOx level out of the catalyst. Based on the engine out and the tail pipe out NOx sensor values, the flow rate of DEF will adjust to meet the NOx allowed per regulations.NOx Sensors
Illustration 5 g06183118
(22) Electrical connector
(22) Sensor electronic control unit
(24) Cable (black for engine out, gray for CEM out)
(25) Sensing unitThe NOx sensor contains a sensing element, a harness, and an electronic control unit. The sens