I have a '98 E320 Wagon with about 86,000 miles. The check engine light came on last month, so I took it to my mechanic and the trouble code was P0422 (catalytic converter). He reset the code and all was well for about a week and the light came on again. The same code came up, he reset it again and it lasted a few days this time. After a few days of the light being on, it went out by itself. About a week later, the light came on again.

Given the high price (PartsShop MUCH less expensive than dealer) of a replacement converter I would like to make sure it is really the problem before I replace it. If I really do need to replace it, the mechanic has two conflicting code documents: one says driver's side converter, the other says cylinder bank one, which could be the passenger side.

Any suggestions or help would be appreciated!