S07.10-0039-79
Block diagram |
A1/1 | Instrument cluster (KI) control unit | Y49/11 | Exhaust camshaft solenoid | |
A1/1e58 | Engine diagnosis indicator lamp | CAN HMI | User interface CAN | |
B70/2 | Crankshaft Hall sensor | CAN V | Vehicle CAN | |
G3/1 | Oxygen sensor downstream of catalytic converter | A | Mercedes-Benz | |
G3/2 | Oxygen sensor upstream of catalytic converter | B | Nissan | |
N3/34 | ME-SFI [ME] control unit | C | Default | |
N93 | Central gateway (CGW) | D | Optional | |
Y49/10 | Intake camshaft solenoid |
Function requirements for exhaust aftertreatment, general points
Circuit 87 ON (engine management ON)
Engine running.
Exhaust aftertreatment, general points
The task of the exhaust aftertreatment is to reduce the exhaust emissions:
Nitrogen oxides (NOx)
Hydrocarbons
Carbon monoxide (CO)
The ME-SFI [ME] control (N3/34) determines the valve overlap by triggering the intake camshaft actuator solenoid (Y49/10) and the exhaust camshaft actuator solenoid (Y49/11). Thereby controlling the exhaust gas recirculation rate of the internal exhaust gas recirculation.
Exhaust aftertreatment, function sequence
The exhaust gas post treatment is described in the following paragraphs:
Function sequence for catalytic converter
Function sequence for monitoring the catalytic converter efficiency
Function sequence for catalytic converter
Through oxidation, carbon monoxide is converted to carbon dioxide (CO2) and hydrocarbon to water (H2O) + carbon dioxide.
Through reduction the nitrogen oxides are converted into nitrogen (N2) + carbon dioxide.
Additional function requirements for monitoring the catalytic converter efficiency
Catalytic converter at operating temperature
Lambda control released
Function sequence for monitoring the catalytic converter efficiency
By law, hydrocarbon emissions must not go above prescribed limits.
The purpose of monitoring the catalytic converter efficiency is to use the oxygen storage capacity of the catalytic converter to determine the degree of aging, and therefore the degree of hydrocarbon conversion.
For monitoring the catalytic converter operation, the ME controller (N3/34) reads in the signals from the following sensors:
Oxygen sensor downstream of catalytic converter (G3/1)
Oxygen sensor upstream of catalytic converter (G3/2)
Crankshaft Hall sensor (B70/2)
The oxygen stored during an operating phase with lean mixture is wholly or partly reduced in an operating phase with rich mixture. Aging reduces the oxygen storage capacity and hydrocarbon conversion capacity of the catalytic converter. Due to the three-way catalytic converter's high oxygen storage capacity, the change in oxygen content is nearly fully dampened downstream of the three-way catalytic converter. Consequently, the oxygen sensor signal downstream of the catalytic converter has a low amplitude and is virtually constant.
When the catalytic converter is at operating temperature and the lambda control enabled, the amplitude variables of the oxygen sensor signals downstream and upstream of the catalytic converter are compared.
If the catalytic converter is no longer ready for operation, the oxygen sensor signal from the oxygen sensor upstream of the catalytic converter (G3/2) and the oxygen sensor signal from the oxygen sensor downstream of the catalytic converter (G3/1) are the same.
A number of measurements take place in the lower partial-load range in the specified rpm range.
Detected faults are stored in the fault memory of the ME-SFI control (N3/34).