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

ENGINE 651.9 in MODEL 207, 212 (except 212.098/298), 218 

with CODE U77 (Diesel Emission control BLUETEC (SCR)) 

without CODE 494 (US version) 

without CODE U42 (BlueTEC diesel exhaust treatment (SCR)) 

Shown: model 212.0 at front left 

Fig 1: AdBlue® Control Unit

Courtesy of MERCEDES-BENZ USA

Location 

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

Task 

The AdBlue® control unit controls the following tasks according to a characteristics map:

• AdBlue® delivery
• Fuel injection
• Antifreeze protection and recirculation

Input and output signals 

The following input signals are evaluated by the AdBlue® control unit and the respective output signal is issued:

• Direct input signals 
• Direct output signals 
• CAN input signals 
• CAN output signals 

Direct input signals 

• Circuit 31
• Circuit 30, over circuit 87 relay for the AdBlue® supply (K277)
• Sensor signal of AdBlue® fill level sensor (A103/1b5)
• Sensor signal of AdBlue® container temperature sensor (A103/1b1)
• Recording 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 modulated signal for actuation of the AdBlue® delivery pump
• Pulse width modulated signal for actuation of the AdBlue® metering valve (Y129)
• Power supply for the AdBlue® container heating element (A103/1r1)
• Power supply for the 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 time of the AdBlue® control unit
• Diagnosis request

CAN output signals 

CDI control unit

• Reduction agent quantity to be injected for NOx 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 reduction agent for nitrogen oxide (NOx) reduction. The delivery pressure is adjustable by the control unit software and can be different according to the 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 NOx reduction

Antifreeze protection and recirculation 

• After "circuit 15 ON", the pump is given an initial run (warm-up) if the weather is cold. The pump flow serves to remove the friction in the case of cold, so that the desired pressure can be made available as soon as possible after the pressure request.
• Actuation of the AdBlue® tank heating element to liquefy the AdBlue® reduction agent in the AdBlue® tank, which freezes at about -10 °C
• Actuation of the AdBlue® pressure line heating element to guarantee flowability of the AdBlue® reduction agent, which freezes at about -10 °C, in the AdBlue® 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 heating of the metering valve.

The duration of the return delivery of the AdBlue® reduction agent and the duration of the pressure line filling depend on the length of the AdBlue® pressure line.

The quantity of reduction agent injected by AdBlue® the metering valve is sent by the AdBlue® control unit via the drive train sensor CAN (CAN I) to the CDI control unit. This quantity of reduction agent is taken into account for the following computation of the necessary reduction agent quantity by the CDI control unit.