Cadillac CTS First Generation Forum - 2003 - 2007 Discussion, O2 Sensor in Cadillac CTS Coupe, Sport Sedan and Sport Wagon Forums; I have the dreaded check engine light. I pulled the codes and I have P0158 Mod$11 O2 Sensor Circuit High ...
I have the dreaded check engine light. I pulled the codes and I have P0158 Mod$11 O2 Sensor Circuit High Voltage Bank 2 Sensor 2. How hard is it to change and where is it? I have worked on early GMs and remember only having 1 O2 sensor.
There will be one in front of each Cat and one behind each cat. They're accessible from under the car, pretty easily. I believe Bank 2 Sensor 2 is the rearmost passenger side sensor. But if one is going bad (due to eventual carbon buildup), then they're all going to do the same thing soon. Most manufacturers recommend changing them every 100k miles (some at 60K!). Most people I know don't' change them until the check engine light comes on. The O2 sensor isn't just for emissions. It's part of the feedback loop on the fuel injection that measures combustion efficiency.