Question: I have a 2001 Jeep Grand Cherokee with the 4.0-liter six-cylinder and about 120,000 miles. I keep getting a catalytic converter code P0420. I heard there may be a way to fix it by ...

P0420 code represents “Catalyst System Efficiency Below Threshold, Bank 1.” It is usually, but not always, caused by a bad converter that’s not reducing emissions output as it should.