Exhaust treatment function - GF14.00-P-3000MMY

ENGINE 157.9, 278.9 in MODEL 166 as of model year 2016 

ENGINE 157.9, 278.9 in MODEL 292 

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 (NOx)
• Hydrocarbon (HC)
• Carbon monoxide (CO)

To do this, amongst other things, the firewall catalytic converter 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 firewall catalytic converters 
• Function sequence for upshift delay 
• Function sequence for monitoring the catalytic converter efficiency 

Function sequence for firewall catalytic converters 

The pollutants in the exhaust emitted by the engine are converted chemically by the near-engine mounted catalytic converters (three-way catalytic converters) for λ=1.

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 for a 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 the chassis CAN 1 (CAN E1)

The upshift delay is active for a maximum of 60 s and exclusively occurs electronically.

The ME-SFI [ME] control unit makes a request to the fully integrated transmission control unit (Y3/8n4) via the drive train CAN (CAN C) to shift the shift characteristic curves.

Partial load gear shifts (1-2-1, 2-3-2) thus take place at higher engine speeds or at higher vehicle speeds.

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 [ME] control unit reads in the following signals to monitor the catalytic converter efficiency:

• Oxygen sensor elements at left and right upstream of catalytic converter (G3/3b1, G3/4b1), residual oxygen content
• LH and RH oxygen sensor elements downstream of catalytic converter (G3/5b1, G3/6b1), residual oxygen content
• Crankshaft Hall sensor (B70), engine RPM

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.

Changes in the oxygen content downstream of the catalytic converters are almost completely dampened by the high oxygen storage capacity of the catalytic converters. Consequently, the signals from the oxygen sensor elements downstream of the catalytic converters have low amplitude and are virtually constant.

If the catalytic converters are no longer ready to operate then the signals from the oxygen sensor elements upstream of the catalytic converter and the signals from the oxygen sensor element downstream of the catalytic converter are the same size. 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 there is fault detection the ME-SFI [ME] control unit actuates the engine diagnosis indicator lamp (A1e58) in the IC (A1) via the chassis CAN 1 and chassis CAN 2 (CAN E2).

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

Electrical function schematic for exhaust treatment	PE14.00-P-2051-97NBB
Overview of system components for gasoline injection and ignition system with direct injection	GF07.70-P-9998MNG