Catalytic Converter Efficiency Monitor Function

USA Version With code (494a)

Shown On Engine 104 (USA):

Shown On Engine 166 EURO3:

Task
Detecting catalytic converters with inadequate efficiency and actuating engine diagnosis malfunction indicator lamp (EUR03/4) or CHECK ENGINE (USA) MIL

Design/function
If the catalytic converter is at its normal operating temperature and the lambda control is active, the O2 sensor signal downstream of TWC is compared with the O2 sensor signal upstream of TWC. The amplitude of the O2 sensor voltage downstream of TWC must be less than the amplitude of the 02 sensor voltage upstream of TWC (note: If, for example, no monolith were installed in the catalytic converter, the O2 sensor signals upstream and downstream of TWC would be identical).

The catalytic converter is assessed by means of its ability to store oxygen. Several measurements must be performed at the specified engine speed and load range. The results are compared with a map and any fault detected in this way.

ME-SFI control module position/ task/ design/ function
- M111 EURO3/4

ECM control module position/task/design/function
- Hot film mass air flow sensor and intake air temperature sensor integrated