My check engine light just came on, i took it in and the inspection Revealed the following: Diagnostic trouble code P0421 Catalytic Converter efficiency B1-current and pending. Tested B1S1 and B1S2 Oxygen Sensor on lab scope. Rise and flatten good. B1S2 follows B1S1 identically. Recommend replace B1 Catalytic Converter (passenger side).

I have a California car with 3 catalytic converters. The stealership wants $757.15 for the catalytic converter (part number MR340040). The cheapest I have found it online is $536.90 (http://ricartmitsubishiparts.com). Here is the qestion, Kragen sells an aftermarket universal fit catalytic converter for $90 will that work?


Also where can I find a good service manual for my car?

There are many posts about this on here. Most times to almost always its the HO2 sensors (heated oxygen sensors) after the catalytic convertors that are teh actual issue. But the 2 sensors after the catalytic convertor are not the same. Altho parthouses will call for the same sensor after , the left and right bank HO2S are actually 2 diffrent sensors

they checked the 2 oxygen sensors (B1S1 & B1S2) related to the fault code and they both appeared to be working properly. Could you be more specific as to what else I should have done to inspect the oxygen sensors? If both sensors are operating properly is there anything else I should check before I replace the catalytic converter?

Catalyst efficiency issues are tricky , in just about all my cases it has lead to the downstream heated oxygen sensor after the catalytic converter . The rear HO2 sensors , they must get and stay within the right heat range during engine situations.

Crystlization around the outer part of the sensor can cause and issue as the flow of exhaust air over the sensor will not be correctly read and the sensor will not read proper heat temps. This also can be in case of the sensor working properly but with a crystalized exterior it cant pick up correct readings.

Other catalytic efficiency if nothing to do with the sensor , would have to be as in a clogged catalytic convertor which in most cases would not be both at teh same time and would be fairly noticable , a lean bank code would be preexisting to this issue also.

If the catalytic was failing in a way that too high a flow of air was streaming thru to the downstream HO2S after the catalytic , a rich bank code would be emitted to one or both banks and then a catalist effeciency.