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

ENGINE 642.8 in MODEL 207 with CODE U77 (Diesel Emission control BLUETEC (SCR)) 

ENGINE 642.8 in MODEL 212 as of 9/1/14, 218 as of 9/1/14 with CODE U77 (Diesel Emission control BLUETEC (SCR)) 

Shown on model 212.024 from the rear 

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 based on 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 corresponding output signals issued:

• Direct input signals 
• Direct output signals 
• CAN input signals via the drive train sensor CAN (CAN I) 
• CAN output signals via drive train sensor CAN 

Direct input signals 

• Circuit 31
• Circuit 30, over circuit 87 relay for the AdBlue® supply (K277)
• Sensor signal from AdBlue® pressure sensor (A103/2b1)
• Sensor signal from "Full" fill level sensor (A103/1b2)
• Sensor signal from "Reserve" fill level sensor (A103/1b3)
• Sensor signal from "Empty" fill level sensor (A103/1b4)
• 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 for circuit 31 for the AdBlue® supply relay
• Common power supply for circuit 30 of the AdBlue® delivery pump and the AdBlue® switchover valve (A103/2y1)
• Supply of circuit 31 for the AdBlue® delivery pump
• Pulse width modulated signal for actuation of the AdBlue® delivery pump
• Control signal circuit 31 for actuation of AdBlue® switchover valve
• 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 AdBlue® delivery module heating element (A103/2r1)
• Power supply for the AdBlue® pressure line heating element (A103/1r2)

CAN input signals via drive train sensor CAN 

CDI control unit (N3/9)

• Request for reduction agent injection
• Specification of the reduction agent quantity to be injected
• Specification of the run-on time of the control units
• Diagnosis request

CAN output signals via drive train sensor CAN 

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 line 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® delivery pump to generate a pressure of 5 bar before and during injection of the reduction agent for cooling the AdBlue® metering valve
• 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 injection of the reducing agent for NOx reduction and for cooling the AdBlue® metering valve

Antifreeze protection and recirculation 

• 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® feed unit heating element and AdBlue® pressure line heating element to ensure flowability of the AdBlue® reduction agent (which freezes at about -10°C) in the AdBlue® feed module (A103/2) and in the pressure line to the AdBlue® metering valve
• Actuation of the AdBlue® delivery pump, AdBlue® reversing valve and AdBlue® metering valve to return the AdBlue® reduction agent from the pressure line to the AdBlue® tank during power-down of the AdBlue® control unit after "circuit 15 OFF"

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

The quantity of reduction agent injected by the AdBlue® metering valve is sent by the AdBlue® control unit via the drive train sensor CAN to the CDI control unit.