Monitoring catalytic converter efficiency, function - GF49.10-P-3033G
ENGINE 273 in MODEL 463.202 /222 /236 /237 up to 31.5.12 as of Model Year 2009 /YoM 08
Function requirements for monitoring catalytic converter efficiency, general points
- Circuit 87M ON (engine control ON)
- Engine running
- Firewall catalytic converters at operating temperature
- Lambda control enabled
Monitoring catalytic converter efficiency, general points
Hydrocarbon (HC) emissions should not exceed the limit specified by the legal requirements. The tasks of monitoring is to obtain a statement from the oxygen storage capacity of firewall catalytic converters about their aging and thus about the HC conversion.
To do this, the ME-SFI [ME] control unit reads the following sensors:
- Crankshaft Hall sensor (B70), engine speed
- LH and RH O2 sensors upstream of catalytic converter, signals from oxygen sensors upstream of catalytic converter
- LH and RH O2 sensors downstream of catalytic converter, signals from oxygen sensors downstream of catalytic converter
The oxygen stored during the "lean operating phase" is then reduced totally or partially during the "rich operating phase". With aging, the oxygen storage capacity of firewall catalytic converter 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.
Monitoring catalytic converter efficiency, function sequence
When firewall catalytic converters are at operating temperature and the lambda control is enabled, the signal amplitudes of the oxygen sensors upstream of the firewall catalytic converters are compared with those downstream.
If the firewall catalytic converters are no longer operational, the oxygen sensor signals from the O 2 sensors upstream and from the O2 sensors downstream of the CAT are the same size.
A number of measurements take place in the lower partial-load range in the specified engine rpm range.
The results are compared with a performance map in the ME-SFI [ME] control unit.
Any faults detected are stored in the fault memory of the ME-SFI [ME] control unit. These can be read out and deleted with the Diagnosis Assistance System (DAS).
In the case of fault detection the ME-SFI [ME] control unit actuates the engine diagnosis indicator lamp or the CHECK ENGINE indicator lamp in the instrument cluster via the drive train CAN.
| Component description for ME-SFI [ME] control unit | N3/10 | GF07.61-P-6000G |