Diesel Exhaust Fluid Components - EU6 And NAS Only
Diesel Exhaust Fluid Tank Module
| ITEM | DESCRIPTION |
|---|---|
| 1 | Diesel Exhaust Fluid (DEF) tank module |
| 2 | DEF line heater |
The Diesel Exhaust Fluid (DEF) tank module is located at the bottom of the DEF tank. The DEF tank module includes a DEF level and temperature sensor and a heater element to defrost the DEF in extreme cold climates.
The DEF level sensor is an ultrasonic device located in the DEF tank module. The DEF level sensor sends the DEF level value to the Powertrain Control Module (PCM) via Pulse Width Modulation (PWM) signals. The Negative Temperature Coefficient (NTC) temperature sensor measures the temperature of the fluid in the DEF tank. Similar to the ultrasonic DEF level sensor, the temperature sensor transmits the initial temperature signal to an evaluation unit in the DEF tank module. The evaluation unit converts the signal into a PWM signal and sent to the PCM for processing.
The heater element is a Positive Temperature Coefficient (PTC) type heater. Under normal operation the maximum current is 6A. The heater element is designed to defrost the DEF in extreme cold climates. The element is a PTC heater that is intrinsically safe to operate. A feature of this design is that the current drawn from the electrical power supply reduces as the temperature of the element increases.
The DEF tank module receives a 12V power supply from a DEF relay located in the Rear Junction Box (RJB). The DEF relay is controlled by the PCM via power supplied from the PCM relay in the RJB.
The DEF tank module and the DEF heater control unit are connected to the PCM via a private Controller Area Network (CAN) bus.
The PCM controls the DEF injection pump which comprises two solenoid pumps within the DEF tank. One pump supplies pressurized DEF to the DEF injector. The second pump purges DEF from the DEF injector supply line to prevent freezing in cold climates. Both pumps are controlled by a ground connection from the PCM.
The DEF line heater receives a 12V power supply from the DEF heater control unit. The DEF heater control unit receives a battery supply via the RJB. The DEF line heater provides heating of the DEF as it passes from the DEF tank to the DEF injector in cold conditions.
The DEF heater control unit also controls the heater element in the DEF tank module.
Diesel Exhaust Fluid Tank Module
The Diesel Exhaust Fluid (DEF) heater control unit is located in the luggage compartment. The DEF heater control unit is located on a stud on the rear right wheel arch reinforcing panel and secured with a nut.
The DEF heater control unit receives a permanent 12V battery supply via the Rear Junction Box (RJB). A second supply is provided via the Powertrain Control Module (PCM) relay in the Engine Junction Box (EJB).
The DEF heater control unit provides current information for each heater power stage on a private Controller Area Network (CAN) bus to the PCM. Any faults detected are stored in the PCM fault memory and can be retrieved with approved diagnostic equipment.
The DEF line heater receives a power supply from the DEF heater control unit. The DEF line heater provides heating of the DEF as it passes from the DEF tank to the DEF injector in cold conditions.
The heater element in the DEF tank module receives a power supply from the DEF heater control unit. The heater element provides heating of the DEF in the DEF tank.
Diesel Exhaust Fluid Injector
The Diesel Exhaust Fluid (DEF) injector is located in the exhaust system, downstream of the Diesel Particulate Filter (DPF). The DEF injector delivers a metered amount of DEF into the exhaust pipe.
The DEF injector works at high pressures to provide complete atomization of the injected DEF. This make sure that the Selective Catalyst Reduction (SCR) catalytic converter performs at its optimum performance.
The DEF injector is activated by a Pulse Width Modulation (PWM) signal, controlled by the Powertrain Control Module (PCM). A signal duty cycle of 3.33 - 4 Hz determines the opening duration of the DEF injector. The DEF injector is designed to operate at a nominal operating pressure of 4.4 and 8.6 bar (64 and 125 psi).
Heat, generated by the exhaust system, is dissipated through the DEF injector by cooling fins built into the body of the DEF injector.