3R0-77101-1 Tohatsu CYLINDER PIN LOWER

Illustration 1 g03690311
Typical example
(1) Exhaust inlet from back pressure valve
(2) Selective Catalytic Reduction (SCR) system
(3) Exhaust out
(4) Ammonia sensor (if equipped)
(5) Nitrogen Oxide (NOx) sensor
(6) Diesel Exhaust Fluid (DEF) injector
(7) Diesel Exhaust Fluid (DEF) supply line
(8) Diesel Exhaust Fluid (DEF) pump and dosing control unit
(9) Coolant supply from engine line
(10) Coolant diverter valve
(11) Diesel Exhaust Fluid (DEF) tank
(12) Coolant supply connector
(13) Suction connector
(14) Backflow connector
(15) Coolant return connector
(16) DEF suction line
(17) Electronic Control Module (ECM)Note: Illustration 1 is a schematic for illustrative purposes only. Ensure that the diesel exhaust fluid pump is installed to the application in the correct orientation. Refer to Disassembly and Assembly, "Diesel Exhaust Fluid Pump - Remove and Install" for the correct procedure.The Diesel Exhaust Fluid (DEF) Dosing Control System consists of the following components.
Pump Electronics Unit (PEU)
DEF injector
DEF header
Coolant diverter valve
DEF System Heated LinesPump Electronics Unit (PEU)
The Pump Electronics Tank Unit (PEU) consists of the following components.
DEF pump
Dosing Control Unit (DCU)The Dosing Control Unit (DCU) is mounted on the DEF pump assembly.DEF Pump
Illustration 2 g03708834
Typical example
(1) DEF filter
(2) Inlet
(3) OutletThe pump supplies filtered DEF fluid to the DEF injector. The pump consists of inlet port (2) which is the suction side of the pump. The pump then pressurizes the fluid up to 550 kPa (80 psi) and supplies the fluid though outlet port (3). There is a fixed orifice within the DEF injector that governs the return flow from the DEF injector to the tank. This return flow will stabilize the temperature in the DEF injector when the DEF injector is exposed to the hot gases from the exhaust.Once the engine has stopped, the DEF pump will continue flowing in cooling mode to keep the DEF injector cool. Then the DEF pump will proceed to a purge mode. The DEF injector will remain closed. The DEF pump will reverse the flow of the pump and purge the supply, pressure, and return 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 tank and DEF pump.Dosing Control Unit (DCU)This Dosing Control Unit (DCU) is an ECM that controls all the electrical components in the DEF system. While an ECM, this dosing control module is referred to as the DCU. The DCU receives signals from the engine Electronic Control Module (ECM).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 DCU 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 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 g03708818
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 100 micron filter to filter debris from entering the system.DEF ReturnThe DEF is returned back to the tank from the DEF injector.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.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 concentration of the fluid. This is achieved by measuring the time it takes for the emitted ultrasonic signal to be reflected off a known fixed reference point. Based on the chemical properties and temperature of the fluid, 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.There is a configuration parameter in the electronic service tool called "Aftertreatment #1 DEF Quality Sensor Installation Status" that must be programmed to "Installed". The parameter is factory password protected. The DEF tank header with the DEF quality sensor is a data link