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Home >> Mercedes Benz Truck >> 2011 >> ML 350 BLUETEC (164.125) V6-3.0L DSL Turbo (642.820) >> Repair and Diagnosis >> Powertrain Management >> Emission Control Systems >> Diesel Emissions Fluid (DEF) System >> Description and Operation

Diesel Emissions Fluid (DEF) System: Description and Operation




GF14.40-P-3030OGU Component Description For Exhaust After Treatment Control Unit
ENGINES 642.820 in MODEL 164.124 as of model year 2009
- with CODE (U42) BlueTEC (SCR) diesel exhaust treatment / YoM 08 model refinement package
ENGINES 642.820 in MODEL 164.125
- with CODE (494) USA version
- with CODE (U42) BlueTEC (SCR) diesel exhaust treatment
ENGINES 642.820 in MODEL 164.824 as of model year 2009
- with CODE (U42) BlueTEC (SCR) diesel exhaust treatment / YoM 08
ENGINES 642.820 in MODEL 164.825
- with CODE (494) USA version
- with CODE (U42) BlueTEC (SCR) diesel exhaust treatment
ENGINES 642.870 in MODEL 251.124 /125 as of model year 2009
- with CODE (U42) BlueTEC (SCR) diesel exhaust treatment / YoM 08





View of vehicle from the rear on model 251.1

K27/7 AdBlue(R) supply relay
N118/5 AdBlue(R) control unit

Location
The AdBlue(R) control unit is located in the trunk at the bottom right.

Task
The AdBlue(R) control unit controls the following functions based on a characteristics map:
- AdBlue(R) delivery
- Fuel injection
- Antifreeze and recycling

Input and output signals
The following input signals are evaluated by the AdBlue(R) control unit and the corresponding output signals issued:

^ Direct input signals
^ Direct output signals
^ CAN input signals
^ CAN output signals

Direct input signals
- Circuit. 31
- Circuit 30, through AdBlue(R) supply circuit 87 relay (K27/7)
- Sensor signal from AdBlue(R) pressure sensor (A103/2b1)
- "Full" level sensor signal (A103/1b2)
- "Reserve" level sensor signal (A103/1b3)
- "Empty" level sensor signal (A103/1b4)
- AdBlue(R) tank temperature sensor signal (A103/1b1)
- Sensing of the power consumption for diagnosis of the AdBlue(R) delivery pump (A103/2m1)

Direct output signals
- Supply circuit 31 for AdBlue(R) relay supply
- Common supply circuit 30 for AdBlue(R) delivery pump and AdBlue(R) reversing valve (A103/2y1)
- Supply circuit 31 for the AdBlue(R) delivery pump
- Pulse width modulated (PWM) signal for actuation of the AdBlue(R) delivery pump
- Control signal circuit 31 for actuation of AdBlue(R) reversing valve
- PWM signal for actuation of the AdBlue(R) metering valve (Y129)
- Power supply for the AdBlue(R) tank heating element (A103/1r1)
- Power supply for AdBlue(R) delivery module heating element (A103/2r1)
- Power supply for AdBlue(R) pressure line heating element (A103/1r2)

CAN input signals
CDI control unit (N3/9)
- Request for reduction agent injection
- Specification of the reduction agent quantity to be injected
- Specification of the run-on period of the control units
- Diagnosis request

CAN output signals
CDI control unit (N3/9)
- Reduction agent quantity to be injected for NOX reduction
- Reduction agent quantity to be injected for cooling the AdBlue(R) metering valve
- Fill level status in the AdBlue(R) tank
- Requested diagnostic data

AdBlue delivery
- Feed to the AdBlue(R) delivery pump to obtain the operating current consumption as a basis for the diagnosis of the AdBlue(R) delivery pump
- Actuation of AdBlue(R) delivery pump, to generate a pressure of 5 bar before and during the injection of reducing agent for nitrogen oxide (NOX) reduction. The delivery pressure can be set with the control unit software and may differ according to the particular variant.
- Actuation of the AdBlue(R) delivery pump to generate a pressure of 5 bar before and during injection of the reducing agent for cooling the AdBlue(R) metering valve
- Actuation of the AdBlue(R) metering valve for ventilation of the AdBlue(R) pressure line when filling the AdBlue(R) pressure line

Fuel injection
- Actuation of the AdBlue(R) metering valve during injection of the reducing agent for NOX reduction and for cooling the AdBlue(R) metering valve

Antifreeze and recycling
- After "circuit 15 ON", the pump is given an initial run (warm-up) if the weather is cold. The initial run serves to reduce the friction in cold weather, so that, following a demand for pressure, the required compression can be made available as soon as possible.
- Actuation of the AdBlue(R) tank heating element to liquefy the AdBlue(R) reducing agent in the AdBlue(R) tank, which freezes at about -10°C
- Actuation of the AdBlue(R) feed unit heating element and AdBlue(R) pressure line heating element to ensure flowability of the AdBlue(R) reducing agent (which freezes at about -10°C) in the AdBlue(R) feed module (A103/2) and in the pressure line to the AdBlue(R) metering valve
- Actuation of the AdBlue(R) delivery pump, AdBlue(R) reversing valve and AdBlue(R) metering valve, to return the AdBlue(R) reducing agent from the pressure line to the AdBlue(R) tank during power-down of the AdBlue(R) control unit after "circuit 15 OFF"

The duration of the return flow of the AdBlue(R) reducing agent and the duration of the pressure line filling depend on the length of the pressure line.

The quantity of reducing agent injected by the AdBlue(R) metering valve is sent by the AdBlue(R) control unit over the drive train sensor CAN to the CDI control unit. It is taken into account in the next computation of the quantity of reducing agent by the CDI control unit.




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