Fault code description - three-way catalytic converter effectiveness too low - AD07.61-P-4000-16AA

1	Fault code	P200B The efficiency of the right catalytic converter is insufficient.P0422
	( Readout on generic scan tool)	P207E The efficiency of the left catalytic converter is insufficient.P0432
2	Fault storage	after expiry of test duration and fault
	Actuation of the engine diagnosis indicator lamp (EURO3/4) or CHECK ENGINE (MIL) malfunction indicator lamp	following two successive driving cycles with faults
3	Checking frequency	once per driving cycle
4	Checked signal or status	O2 sensor signal downstream of TWC
5	Fault setting conditions  Limit value	The effective O2 sensor signal downstream of TWC must not be greater than a constantly calculated reference signal.
	Checking duration	Approx. 30 seconds
6	Check prerequisites	Engine speed approx. 1800 to 2500 rpm Lambda control enabled No fault in O2 sensors (signal, heater, aging) No high loading of activated carbon filter (lambda greater than 0.4) No misfiring No fault in exhaust gas recirculation No fault in secondary air injection No fault in leaktightness of purge system Load approx. 20% to 50% (12 kg/hour to 150 kg/hour) Catalytic converter temperature greater than 570°C
7		The three-way catalytic converter is evaluated on its ability to store oxygen. The oxygen stored during a lean-mixed phase is either completely or partially consumed during a rich-mixed phase. The storage capacity and thus also the HC conversion are reduced through aging. If the fault codes for the TWC and for the O2 sensors are issued identically, the O2 sensors should be replaced. If then a TWC fault is no longer detected, and if the effect of the three-way catalytic converter has been slightly reduced, it does not need to be replaced yet.

Shown on engine 112 EURO3/4 

Fig 1: Identifying Three-Way Catalytic Converter Components

Courtesy of MERCEDES-BENZ USA