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

ENGINE 651.9 in MODEL 204.9 with CODE U42 (BlueTEC diesel exhaust treatment (SCR)) 

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

Shown on model 212.0 

Fig 1: Adblue Control Unit

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® pressure sensor (A103/2b1)
• Fill level sensor full sensor signal (A103/1b2)
• Fill level sensor Reserve sensor signal (A103/1b3)
• Fill level sensor Empty sensor signal (A103/1b4)
• AdBlue® container temperature sensor signal (A103/1b1)
• Detection of the power consumption for diagnosis of the AdBlue® delivery pump (A103/2m1)

Direct output signals 

• Power supply circuit 31 for AdBlue® power supply relay
• Common power supply for AdBlue® delivery pump circuit 30 and the AdBlue® switchover valve (A103/2y1)
• Power supply for circuit 31 for AdBlue® delivery pump
• Pulse width modulated (PWM) signal for actuation of the AdBlue® delivery pump
• Control signal circuit 31 for actuation of AdBlue® switchover valve
• PWM 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 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
• Power-down period specification for control units
• Diagnosis request

CAN output signals 

CDI control unit 

• Quantity of reduction agent 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 can be set with the control unit software and may differ according to the particular 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 reduction agent for NOX reduction and for cooling the AdBlue® 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 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® delivery module 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, the AdBlue® switchover valve and the AdBlue® metering valve to return the AdBlue® reduction agent from the pressure line to the AdBlue® container 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 depend 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 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 reduction agent by the CDI control unit.