16628-ZV7-000 Honda ROD, CHOKE KNOB (Honda Code 4432183).

Illustration 1 g03414466
Diesel Exhaust Fluid (DEF) dosing control cabinet components
Valves are shown in a static state
(1) Dosing control cabinet
(2) DEF line to injector at CEM
(3) Air line to injector at CEM
(4) Compressed air source (customer supplied)
(5) DEF main tank return line
(6) DEF source (main tank)
(7) DEF pressure sensor
(8) Air assist pressure sensor
(9) Air pressure regulator
(10) Air assist valve (solenoid)
(11) DEF main tank return valve (solenoid)
(12) DEF main tank return valve (pneumatic)
(13) DEF pump The following table is for components located in the dosing control cabinet.
Table 1
Solenoid Valves Pneumatic Valves
System State Air Assist DEF Main
Tank Return DEF Main
Tank Return
Dormant (sleep mode) Closed
Static state Open
Static state Open
Static state
Protect mode against cold (defreeze) Closed Open Open
Preparing dosing readiness
Step 1 Open Open Closed
Preparing dosing readiness
Step 2 Open Closed Open
Preparing dosing readiness
Step 3 Closed Closed Open
Preparing dosing readiness
Step 4 Open Open Closed
Normal dosing operation Open Open Closed
Dormant (sleep mode) Closed Open Closed
Shutoff ( wait for after-run) Open Closed Open For the information contained in Troubleshooting, "Warning Operation", observe the following definitions.Open - Flow of air or flow of DEFClosed - No flow of air or no flow of DEFDormant Sleep Mode
The SCR dosing system is waiting for engine or aftertreatment conditions to be met. The dosing system will enter dormant sleep mode when any of the following are true:
The engine is not running.
Not all aftertreatment electronics are ready.
The dosing control is not requesting DEF flow.Protect Mode Against Cold (defreeze)
The system will enter protect mode against cold for either of the following:
DEF manifold temperature drops below −5° C (23° F)
DEF tank temperature drops below −10° C (14° F)Temperature sensors are monitored to indicate if there is a freeze potential for the DEF. Heaters are utilized to prevent the freezing of DEF.Upon completion of the protect mode against cold, the process will continue on to preparing dosing readiness.DEF Heating System
The DEF heating system uses a combination of heaters. Some heaters are sized to thaw DEF. Some heaters are sized to prevent freezing only of DEF . Freezing will be prevented down to −40° C (−40° F). Component heaters can use external power or generator power during genset operation. To prevent DEF from freezing when the system is powered down, the customer is required to drain the DEF tank. The rest of the system is designed to withstand frozen DEF without a mechanical failure.When powered, the system will maintain DEF temperature to a minimum of −5° C (23° F).The following are monitored by sensors:
DEF tank temperature
DEF manifold temperature
Ambient temperature of the dosing cabinetDEF system components that are heated include the following:
DEF tank
DEF pump
DEF manifold
DEF linesDEF Tank
The customer must provide power to the heater when the engine is shut down, and there is a freeze potential. If power is not provided, the customer is required to drain the DEF tank.DEF Pump
The DEF pump does not require draining when there is a freeze potential.DEF is allowed to freeze in the pump. The heater can thaw frozen DEF within 70 minutes of engine startup.DEF Manifold
The DEF manifold does not require draining when there is a freeze potential.DEF is allowed to freeze in the manifold. The heater can thaw frozen DEF within 70 minutes of engine startup.DEF Lines
DEF line heaters can prevent lines from freezing during engine operation.DEF lines are purged with air when engine shuts down.Preparing Dosing Readiness
The dosing system checks the operation of the air valve, DEF control valves, and DEF dosing pump.The system will annunciate a fault code for any unexpected voltage, current, or pressure values.The system will continue to cycle the valves until all indications determine the system is ready to dose DEF.Step 1
The air assist valve (solenoid) is energized causing the valve to open. The resulting air pressure is measured at the DEF pressure sensor.This action is taken to check for the following conditions:
Blockage in the DEF lines
Stuck DEF main tank return valves
All air lines and DEF lines are present and properly connectedStep 2
The DEF return valve (solenoid) is energized causing the valve to close. This action causes the DEF return valve (pneumatic) to open and the expected result is a drop in pressure at the DEF pressure sensor.If a pressure drop does not result, the DEF return valve may be stuck or a line may be plugged.If a pressure drop does not result, a code will be set and the system will return to the dormant state.Step 3
The air assist valve (solenoid) is de-energized causing the valve to close. This action reduces the back pressure on the DEF dosing pump.The DEF dosing pump is commanded on by the aftertreatment ECM and circulates DEF back into the DEF main tank. This action primes the DEF dosing pump.Step 4
The DEF return valve (solenoid) is de-energized causing the valve to open.This action causes the DEF return valve (pneumatic) to close resulting in the pump priming DEF to the injector.Once DEF pressure indicates a complete system prime, the SCR dosing system will move on to normal dosing operation.If the system fails to build sufficient pressure in step 4, the system will return to step 3 multiple times in an attempt to build pressure. If the system still cannot build pressure, a code will be set and the system will return to the dormant state.Normal Dosing Operation
If the exhaust temperature has reached 200° C (392° F), the minimum for NOX reduction to occur, dosing will begin. During normal dosing operation DEF is supplied to the injector by the dosing pump. The desired rate of DEF injection is determined via a closed loop system, utilizing NOX sensors for feedback. The sensors measure the level of nitrogen oxide in the exhaust gas exiting the Clean Emissions Module (CEM). The rate of injection is controlled by the aftertreatment ECM that varies the frequency of a command signal to the dosing pump. The dosing system will go to the shutoff system state and activate a