Catalyst system efficiency below threshold ban 2.
Bank 2 is the bank of cylinders which does not include the #1 cylinder. You have a separate catalytic converter for each bank of 3 cylinders of your v6. So you have two. Each has an oxygen sensor before and after the car con and the car's computer monitors the output of both to determine if the catcon is efficiently doing its job How many miles on the car? There are several possibilities of what's going on: The sensor after the catcon is fouled and reading incorrectly, causing the efficiency calc to be incorrect. The upstream sensor is fouled, sensing less oxygen than it should, making the fuel mix too rich, burning moe gas and making the efficiency calc incorrect. All of the catalyst in your catcon has been used up, and the catcon can no longer do it's job. This can be checked in two ways. One is to measure the exhaust temp difference from front of the catcon to the back. If there is no temp difference the catcon is usually gone. The behavior; of the front and rear O2 sensors will track temporally with each other and I believe the sensor readings themselves will be pretty close. This indicates that whatever is getting to the Catcon and going through is doing so unchanged as the oxygen level is not changing after the exhaust goes through the catcon . If one catcon is dead, the other is not far behind in most cases so you may consider getting both replaced if that is indeed the required action.
