Hello Friends,

Im a new guy here and I have a 2003 Mistubishi Galant ES, 4 Cylinder with 104,000 miles on it. Recently I had error code P0421 on it, which apparently is the most common issue for Mitsubishis. I spoke to a local mechanic and he said that this model has 2 catclytic converters (one at the bottom of the car and the other in the hood near the engine). He suggested me to change the bottom one as it is cheaper and see what happens. I got that done for $160 and the service engine light came back ON again in just two days. Hence, he now says that the problem is with the catalytic converter in the hood and would cost me $550 to replace.

I wasnt convinced with what he said and I took my car to another mechanic and he ran the OBD and said that the P0421 is for the conveter at the bottom and told that the first mechanic dint replace with the right one. He also said that P0421 is the error code for the converter at the bottom and P0420 is for the one in the hood. Now I am totally confused whom to believe, someone please suggest me what I shoud do and also I highly appreciate you guys if you can throw in some light on which converter to be replaced based on the error code P0421. Thank you very much for your time.