Exhaust treatment function - GF14.00-P-3000MMR
ENGINE 157.9, 278.9 in MODEL 166 up to model year 2016
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 firewall 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 at start < 35°C
- Vehicle speed <40 km/h
Function sequence for upshift delay
The upshift delay brings the firewall catalytic converter more quickly up to operating temperature after the engine start.
The ME-SFI [ME] control unit (N3/10) controls the upshift delay depending on the following sensor and signal:
- Coolant temperature sensor (B11/4)
- Electronic Stability Program control unit (N30/4) wheel speed via the chassis CAN 1 (CAN E1)
Upshift delay is active for a maximum of 60 s and is entirely electronic. The ME-SFI [ME] control unit makes the request via the drive train CAN (CAN C) to the fully integrated transmission control controller unit (Y3/8) to move the shift characteristics.
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
- Firewall catalytic converters at 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 firewall catalytic converters and thus their HC conversion based on their oxygen storage capability.
The ME-SFI [ME] control unit reads in the following sensors to monitor the catalytic converter efficiency:
- Left and right oxygen sensors upstream of catalytic converter (G3/3, G3/4)
- Left and right oxygen sensors downstream of catalytic converter (G3/5, G3/6)
- 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 firewall catalytic converters is reduced, and so therefore is HC conversion.
Changes in the oxygen content downstream of the firewall catalytic converters are almost completely dampened by the high oxygen storage capacity of the firewall catalytic converters.
Consequently, the signals from the oxygen sensors downstream of firewall catalytic converters have low amplitude and are virtually constant.
When firewall catalytic converters are at operating temperature and the lambda control is enabled, the signal amplitudes of the oxygen sensor downstream and upstream of the firewall catalytic converters are compared.
If the firewall catalytic converters are no longer working effectively, the oxygen sensors signals upstream of catalytic converter have the same amplitude as those downstream.
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, chassis CAN 1 (CAN E1) and chassis CAN2 (CAN E2) are used by the ME-SFI [ME] control unit to actuate the engine diagnosis indicator lamp (A1e58) in the instrument cluster (A1). 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-2051-97NAF |
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MMG |