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

Engine 176.9, 177.9 in model 217 

Engine 176.9, 177.9 in model 222 

Engine 177.9 in model 290 

up to model year 2021 

Function requirements for exhaust treatment, general points 

• Circuit 87M (Engine management ON)
• Engine runs

Exhaust treatment, general 

The task of exhaust treatment is to reduce the exhaust emissions:

• Nitrogen oxides (NO _x )
• Hydrocarbon (HC)
• Carbon monoxide (CO)

To do this, amongst other things, the catalytic converters (three-way catalytic converters) must be rapidly brought up to operating temperature in order to reduce the exhaust emissions for a cold start.

Function sequence for exhaust treatment 

The following subsystems are involved in exhaust treatment:

• Function sequence for catalytic process 
• Function sequence for upshift delay 
• Function sequence for monitoring the catalytic converter efficiency 

Function sequence for catalytic process 

The pollutants emitted by the engine are converted chemically at λ = 1 by the catalytic converters (three-way catalytic converters).

Through oxidation, carbon monoxide is converted to carbon dioxide (CO₂ ) and hydrocarbon to water (H₂ O)+ carbon dioxide.

Through reduction the nitrogen oxides are converted into nitrogen (N₂ )+ carbon dioxide.

Additional function requirements for upshift delay 

• Coolant temperature at start < 35°C
• Vehicle speed < 40 km/h

Function sequence for upshift delay 

The upshift delay is designed to warm up the catalytic converters to operating temperature more rapidly after the engine has started.

The ME-SFI [ME] control unit (N3/10) controls the upshift delay dependent on the following signals:

• Coolant temperature sensor (B11/4), coolant temperature
• Electronic Stability Program control unit (N30/4), wheel speed via suspension FlexRay (Flex E), powertrain control unit (N127) and drive CAN (CAN C1)

Upshift delay is active for a maximum of 60 s and is entirely electronic. Via the drive CAN, the ME-SFI [ME] control unit requests the fully integrated transmission control unit (Y3/8n4) (models 217, 222) or the control unit for the fully integrated transmission control electric controller unit (Y3/8n4) (model 290) to move the shift curves.

The partial load shifts then occur at a higher motor rpm or higher vehicle speed.

Additional function requirements for monitoring the catalytic converter efficiency 

• Catalytic converters at normal operating temperature
• Lambda control released

Function sequence for monitoring the catalytic converter efficiency 

Hydrocarbon (HC) emissions must not exceed the limit specified by the legal requirements.

The task of the catalytic converter efficiency monitoring function is to determine the aging of the catalytic converters and thus their HC conversion based on their oxygen storage capability.

The ME-SFI control unit reads in signals from the following sensors to monitor the catalytic converter efficiency:

• Left and right oxygen sensor elements upstream of catalytic converter (G3/3b1, G3/4b1)
• LH and RH oxygen sensor elements downstream of catalytic converter (G3/5b1, G3/6b1)
• Crankshaft Hall sensor (B70), engine speed

The oxygen stored during the "lean operating phase" is reduced totally or partially during the "rich operating phase". With aging, the oxygen storage capacity of the catalytic converters is reduced, and thus also HC conversion.

Due to the catalytic converters' high oxygen storage capacity, the change in the oxygen concentration is nearly fully dampened downstream of the catalytic converters.

Consequently, the signals from the lambda sensors downstream of the catalytic converters have low amplitude and are virtually constant. When catalytic converters are at operating temperature and the lambda control is enabled, the signal amplitudes of the lambda sensors upstream of the catalytic converters are compared with those downstream.

If the catalytic converters are no longer functional, then the lambda sensor signals of the sensor elements for the lambda sensors upstream of the catalytic converter and the lambda sensor signals of the sensor elements for the lambda sensors downstream of the catalytic converter are the same magnitude.

A number of measurements take place in the lower partial-load range in the specified rpm range. The results are compared with a characteristics map in the ME-SFI [ME] control unit

If a fault is detected, the engine diagnosis control message in the instrument cluster (A1) is actuated via the drive CAN, the powertrain control unit, the suspension FlexRay, the electronic ignition lock control unit (N73), and the user interface CAN (CAN HMI).

Any faults detected are stored in the fault memory of the ME-SFI control unit. These can be read out and deleted with XENTRY Diagnostics.

	Electrical function schematic for exhaust treatment	Engine 177.9 in model 290 up to model year 2021	PE14.00-P-2051-97XBA
		Engine 176.9, 177.9 in model 217 Engine 176.9, 177.9 in model 222	PE14.00-P-2051-97SEL
	Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-P-9998MNL