LEMON Manuals: Even more car manuals for everyone
Home >> Mercedes Benz >> 2017 >> GLC300 Base >> Repair and Diagnosis >> Engine Mechanical >> Mechanical >> Exhaust Manifold, Emission Control System - 253 Chassis >> Basic Knowledge >> Exhaust Treatment Function >> Exhaust Treatment Function - GF14.00-P-3000MNA

Exhaust Treatment Function - GF14.00-P-3000MNA

Engine 177.9 in model 205, 213, 253 

Function requirements for exhaust treatment, general points 

IMPORTANT The ME-SFI [ME] control unit (N3/10) detects the engine running via the evaluation of the crankshaft Hall sensor signals (B70). The ME-SFI [ME] control unit directly reads in the signals of the crankshaft Hall sensor.

Exhaust treatment, general 

The exhaust gas cleaning reduces the harmful components of the combustion gases and residues emitted by the engine.

The following are involved here:

The reduction of the harmful components is achieved by means of reduction and oxidation in the three-way catalytic converter and filtration in the gasoline particulate filter.

For model 213, the gasoline particulate filters are installed with code 472 (gasoline particulate filter) or code 598 (gasoline particulate filter (OPF) with sensor system).

Exhaust gas cleaning in three-way catalytic converter 

For a three-way catalytic converter, the operating temperature is decisive. Significant pollutant conversion only begins from an operating temperature of about 250°C.

Ideal operating conditions for high conversion rates and a long service life exist in the temperature range between approx. 400 and 800°C. To reach this temperature quickly, the switch points are increased for a maximum of 60 s during a cold start (coolant temperature < 35°C). However, upshift delay is active only up to a speed of 40 km/h. The gears are therefore not shifted up until higher rotational speeds are reached.

Depending on the coolant temperature and wheel speed, the ME-SFI [ME] control unit transmits the upshift delay to the fully integrated transmission control unit (Y3/8n4) via the drive CAN (CAN C1). The ME-SFI [ME] control unit reads in the signals of the coolant temperature sensor (B11/4) directly.

The Electronic Stability Program control unit (N30/4) transmits the wheel speed to the ME-SFI [ME] control unit via the suspension FlexRay (Flex E), the powertrain control unit (N127) and the drive CAN.

The chemical conversion takes place in the three-way catalytic converter at λ = 1.

Through oxidation, the carbon monoxide (CO) is converted into carbon dioxide (CO2 ) and the hydrocarbon (HC) into water (H2 O) and carbon dioxide (CO2 ).

Through reduction, the nitrogen oxide (NOx ) is converted into nitrogen (N2 ) and carbon dioxide (CO2 ).

Once the operating temperature is reached and lambda control has been enabled, the function of the three-way catalytic converter is monitored by the ME-SFI [ME] control unit.

For this purpose, the ME-SFI [ME] control unit reads in the signals from the following component parts:

The ME-SFI [ME] control unit assesses the oxygen storage capacity of the three-way catalytic converter and, with that, assesses its aging.

IMPORTANT Any oxygen exceeding the amount required for the three-way catalytic converter to oxidize carbon monoxide (CO) is stored. If the oxygen present in the exhaust gas is not sufficient for oxidizing the carbon monoxide (CO), the stored oxygen is fully or partially removed. In combination with the high oxygen storage capacity of the three-way catalytic converter, this procedure achieves an almost complete compensation for the fluctuations in oxygen concentration upstream of the three-way catalytic converter. The oxygen storage capacity, and thus the function of the three-way catalytic converter, can be assessed on the basis of the lambda sensor signals upstream and downstream of the three-way catalytic converter. In the case of a fully functional three-way catalytic converter, high values and changes are measured upstream and downstream of the three-way catalytic converter. In contrast, the lambda sensor signal downstream of the three-way catalytic converter is virtually constant. As the aging process advances, the oxygen storage capacity of the three-way catalytic converter, and thus its ability to convert carbon monoxide (CO) and hydrocarbons (HC), is reduced.

Consequently, the lambda sensor signal downstream of the three-way catalytic converter becomes increasingly similar to the lambda sensor signal upstream of the three-way catalytic converter.

The lambda sensor signals upstream and downstream of the three-way catalytic converter are compared. If both signals are almost identical, the three-way catalytic converter is no longer operational. Multiple measurements are performed in the lower partial-load range at specified rotational speeds. The results are compared with a characteristics map in the ME-SFI control unit.

Where a defect is detected, a fault message is output in the instrument cluster (A1). In vehicles except code 464 (Digital instrument cluster full display), the engine diagnosis indicator lamp (A1e58) is actuated for this purpose. In vehicles with code 464 (Digital instrument cluster full display), the fault message is output directly in the instrument cluster. The ME-SFI [ME] control unit transmits the request for the fault message output to the instrument cluster via the drive CAN, powertrain control unit, suspension FlexRay, electronic ignition lock control unit (N73) and user interface CAN (CAN HMI). Recognized fault are stored in fault memory of the ME-SFI [ME] control unit. These can be read out and deleted with the vehicle diagnosis system.

Exhaust gas cleaning in the gasoline particulate filter (model 213 with code 472 (gasoline particulate filter) or code 598 (gasoline particulate filter (OPF) with sensor system)) 

The gasoline particulate filter absorbs the emitted soot particles and regenerates itself under specific operating conditions.

The regeneration (soot combustion) of the gasoline particulate filter takes place while the vehicle is being operated in a conventional driving style, predominantly in overrun mode. The soot combustion takes place as soon as enough oxygen is available in the gasoline particulate filter.

In the case of model 213 with code 598 (Gasoline particulate filter (OPF) with sensor system), the soot content in the gasoline particulate filters is monitored permanently.

The soot content is determined via the left gasoline particulate filter differential pressure sensor (B163/5) and the right gasoline particulate filter differential pressure sensor (B163/6). The ME-SFI [ME] control unit reads the sensor signals in directly and evaluates them. If the measured values exceed specific limits, the ME-SFI [ME] control unit initiates appropriate interventions in the engine timing and requests a warning message in instrument cluster.

  Electrical function schematic for exhaust treatment Engine 177.9 in model 205, 253 PE14.00-P-2051-97FBD 
Engine 177.9 in model 213 PE14.00-P-2051-97DBG
  Overview of system components for gasoline injection and ignition system with direct injection Engine 177.9 in model 205, 253 GF07.70-P-9998MNA
Engine 177.9 in model 213 GF07.70-P-9998MNE
scientia non olet · About LEMON Manuals