Component description for exhaust aftertreatment control unit - GF14.40-P-3030OME

ENGINE 651.9 as of 9/1/13 in MODEL 212 (except 212.098/298) with CODE 494 (US version) with CODE U77 (Diesel Emission control BLUETEC (SCR)) without CODE U42 (BlueTEC diesel exhaust treatment (SCR)) 

Shown: model 212.0 at front left 

Fig 1: Adblue Control Unit - Shown On Model 212.0

Courtesy of MERCEDES-BENZ USA

Location 

The AdBlue® control unit is located in the trunk at the bottom right.

Task 

The AdBlue® control unit controls the following functions based on a characteristics map:

• AdBlue® delivery
• Injection
• Antifreeze and return flow

Input and output signals 

The following input signals are evaluated by the AdBlue® 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, over circuit 87 AdBlue® power supply relay (K27/7)
• Sensor signal from AdBlue® fill level sensor (A103/1b5)
• AdBlue® container temperature sensor signal (A103/1b1)
• Detection of the power consumption for diagnosis of the AdBlue® delivery pump (A103/2m1)

Direct output signals 

• Supply and actuation of the AdBlue® supply relay
• Supply of AdBlue® delivery pump
• Supply and actuation of the AdBlue® extraction pump (A103/2m2)
• Pulse width modulation (PWM) signal for actuation of the AdBlue® delivery pump
• PWM signal for actuation of the AdBlue® metering valve (Y129)
• Power supply for the AdBlue® container heating element (A103/1r1)
• Power supply for AdBlue® 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 for the run-on period of the AdBlue® control unit
• Diagnosis request

CAN output signals 

CDI control unit 

• Quantity of reduction agent injected for NO_x reduction
• Reduction agent quantity to be injected for cooling the AdBlue® metering valve
• Fill level status in the AdBlue® container
• Requested diagnostic data

AdBlue® delivery 

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

Fuel injection 

• Actuation of the AdBlue® metering valve during the reduction agent injection for NO_x reduction

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 remove the friction in cold weather, so that the required compaction can be made available as soon as possible when pressure is requested.
• Actuation of the AdBlue® container heating element to liquefy the AdBlue® reduction agent in the AdBlue® container, which freezes at about -10 °C
• Actuation of the AdBlue® heating element pressure line to guarantee flowability of the AdBlue® reduction agent, which freezes at about -10°C in the pressure line to the AdBlue® metering valve
• Actuation of the AdBlue® extraction pump for return delivery of the AdBlue® reduction agent in the pressure line in the AdBlue® container during power-down of the AdBlue® control unit after "terminal 15 OFF"
• The AdBlue® metering valve can be actuated without the float needle being opened. This serves to heat the valve.

The duration of the return flow of the AdBlue® reduction 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® metering valve is sent by the AdBlue® control unit over the drive train sensor CAN to the CDI control unit. This quantity is taken into account in the next computation of the quantity of reducing agent by the CDI control unit.