Component description for nitrogen oxides control unit - GF07.70-P-6000MIE

ENGINE 272.982 in MODEL 204.065 

ENGINE 272.983 in MODEL 212.057/257 

ENGINE 272.984 in MODEL 207.357/457 

Front view of exhaust system 

Fig 1: Nitrogen Oxides Control Unit Components - Front View Of Exhaust System

Courtesy of MERCEDES-BENZ USA

Location 

In every exhaust gas system there is an NO _X sensor located with the permanently attached nitrogen oxides control unit. The NO _X sensors are screwed into the exhaust pipe. The nitrogen oxides control unit is located on the underfloor.

Task 

Nitrogen oxides control units are delivered by the company "VDO Automotive AG".

The NO _X sensors detect the NO _X and the O ₂ concentration in exhaust after every NO _X storage catalytic converter and passes this information to the nitrogen oxides control units in the form of voltage signals. These process the information and transmit it via the drive train sensor CAN

(CAN I) to the ME-SFI [ME] control unit (N3/10).

Input and output signals 

The nitrogen oxides control units evaluate the following input signals and send the corresponding output signals:

• Direct input signals 
• CAN input signals from the ME-SFI [ME] control unit 
• CAN output signals to the ME-SFI [ME] control unit 

Direct input signals 

• Terminal 87

CAN input signals from the ME-SFI [ME] control unit 

• Diagnosis requests

CAN output signals to the ME-SFI [ME] control unit 

• NO_X concentration in the exhaust
• O₂ concentration in the exhaust
• Diagnostic data

Design 

Fig 2: Left Nitrogen Oxides Control Unit Components

Courtesy of MERCEDES-BENZ USA

Every NO_X sensor (double chamber sensor with it evaluation circuit) is inseparably connected via an 8-pin sensor line with the nitrogen oxides control unit.

An integral sensor heater which is controlled by the respective nitrogen oxides control unit ensures rapid readiness to operate of the NOx sensors.

Function 

The active ceramic probe bodies consist of many layers with two reaction chambers. The oxygen (O ₂ ) is detected in the exhaust in the first chamber as in the case of an oxygen sensor.

To do this, a pump voltage is applied to the electrodes in the first chamber. This causes the O ₂ molecules to be split into double charged oxygen ions and for them to be pumped out of or into the first contact cavity (depending on whether richer or leaner exhaust gas is present) until a 450 mV voltage difference at the electrodes is reached. The oxygen concentration is calculated from the size of the required pump current "Ip1".

The nitrogen oxide is split at the earth electrode into nitrogen and oxygen in the second chamber if present.

The oxygen is pumped out if the chamber again.

The concentration of the nitrogen oxides in the exhaust is calculated from the resulting pump current "Ip2".

The voltage signals from NO _X sensors are transmitted to the respective nitrogen oxides control unit and processed there. The nitrogen oxides control unit send the NO _X and the O ₂ concentration to the ME-SFI [ME] control unit via the drive train sensor CAN. Using this information the exhaust treatment can be monitored in shift operation (lean-burn operation) of the engine and thus the NO _X storage catalytic converter purging can be controlled.

The NO _X sensors also recognize damage and "sulfur poisoning" of the NO _X storage catalytic converters.

A desulfuring process can be initiated as a reaction by the ME-SFI [ME] control unit by increasing the temperature of the NO _X storage catalytic converters.

Schematic function diagram of the NO  _X  sensor (double chamber sensors) 

Fig 3: NOx Sensor Schematic Function Diagram (Double Chamber Sensors)

Courtesy of MERCEDES-BENZ USA

	Wiring diagram of gasoline direct injection system control unit	N3/10	Vehicle plug model 204	PE07.08-P-2101-97FAB
		N3/10	Vehicle plug model 207	PE07.08-P-2101-97EAD
		N3/10	Vehicle plug model 212	PE07.08-P-2101-97DAD