Exhaust Treatment Function - GF14.00-S-3000TRC
Engine 274 in model 447, 448
except code XM0 (Facelift)
Function requirements for exhaust treatment, general points
- Circuit 87M ON (Engine management ON)
- Engine runs
Exhaust treatment, general
The task of exhaust treatment is to reduce the exhaust emissions:
- Nitrogen oxides (NOx )
- Hydrocarbon (Cx Hy )
- Carbon monoxide (CO)
Y49The ME-SFI [ME] control unit (/34) actuates the intake camshaft solenoid (Y49/10) and the and exhaust camshaft solenoid (N3/11) to determine the valve overlap. The exhaust gas recirculation rate is thereby controlled by internal exhaust gas recirculation.
Function sequence for exhaust treatment
The following subsystems are involved in exhaust treatment:
- Function sequence for catalytic converter
- Function sequence for upshift delay (with an A/T)
- Function sequence for monitoring the catalytic converter efficiency
Function sequence for catalytic converter
The pollutants in the exhaust emitted by the engine are converted chemically by the catalytic converter for a fuel-air/fuel ratio Lambda 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 <50°C
- Vehicle speed < 53 km/h
Function sequence for upshift delay (with an A/T)
The upshift delay brings the CAT downstream of the engine start more rapidly up to operating temperature. The ME-SFI [ME] control unit controls the upshift delay according to the following sensor and signal:
- Coolant temperature sensor (B11/21), coolant temperature over direct line
- Electronic Stability Program control unit (N30/4), wheel speed via the chassis CAN (CAN E)
Upshift delay is active for a maximum of 160 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 electric controller unit (VGS) (N15/11) to move the shift characteristics.
The partial load switchings then take place at a higher vehicle speed.
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.
The ME-SFI [ME] control unit reads in signals from the following sensors to monitor the catalytic converter efficiency:
- Crankshaft Hall sensor (B70/2)
- Oxygen sensor downstream of catalytic converter (G3/21)
- Oxygen sensor upstream of catalytic converter (G8/6)
The oxygen stored during the "lean operating phase" is reduced totally or partially during the "rich operating phase". Aging reduces the oxygen storage capacity and hydrocarbon conversion capacity of the catalytic converter.
Because the catalytic converter has a high ability to store oxygen, the alteration of the oxygen content in line with the catalytic converter is fully dampened.
Consequently, the oxygen sensor signal downstream of the catalytic converter (G3/21) 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 operable, then the oxygen sensor signals upstream of the CAT (G8/6) and the oxygen sensor signal downstream of the CAT are the same size.
The measurements take place in the lower partial-load range and are compared with a characteristics map in the ME-SFI [ME] control unit.
In the case of fault detection the engine diagnosis indicator lamp (A1/1e58) is actuated by the ME-SFI [ME] control unit in IC control unit (IC) (A1/1) via the chassis CAN (CAN E). Recognized fault are stored in 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 | Engine 274 in model 448 except code XM0 (Facelift) | PE14.00-S-2051-97VDC | |
| Engine 274 in model 447 except code XM0 (Facelift) | PE14.00-S-2051-97TRC | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-S-9998TRC |