Last year I slid in snow and did some damage to the undercarriage of my 2011 Kia Soul. The upstream and downstream sensors were replaced and the catalytic converter came apart where the manufacturer welded it and so the mechanic to help me out welded it back together. Ever since then my engine light comes on sporadically and the o2 sensors have been replaced several times now. Last week they found carbon build up so they clean them out and replaced new ones. The light came on again. Could it be the Catylic Converter causing this? They told me that it didn't sound like the converter had any leaks. Please help! They cannot figure out what is happening.