First, some background to the issue...
I recently got a check engine light and a stored P2096 code, which according to my OBD2 scanner and Torque app relates to 'post catalyst fuel trim system too lean bank1'. I cleared the code, but it reappeared about 150 miles later. During a recent visit to Jasmine Porschalink for a seperate issue, I had them check the code on their Durametric and it showed the fault as 'Post catalyst 02 sensor bank 1, ageing'. I am not experiencing and loss of performance or poor idle issues. Fuel consumption has not changed.
In an effort to diagnose the faulty component I have been monitoring the pre and post cat O2 sensors using the graph displays on the Torque OBD2 app, but I need some help understanding the readings. As I understand it, the pre cat voltages should swing between around 0.2v - 0.8v per second (mine appear to do that just fine) and the post cat sensors should output a pretty steadyish 0.7v. Here is where one of mine seem a bit weird. With the engine fully warmed up, Bank 2 post cat sensor outputs a steady 0.7v at idle, but bank 1 is giving unusual outputs. Sometimes it will hold at 0.7v for a minute or two, but then it will seemingly follow the pre cat sensor (not identically, but the voltage swings up and down in a similar fashion). It will then suddenly drop to a steady 0.1v for a minute or two, and so on. These different outputs appear to be random and don't occur in a set order or for a set time. In short, the output is very unpredictable!
I understand that if the post cat sensor follows the pre cat sensor, it is a very good indicator that the cat has failed, but surely if my cat had failed I would not be getting such fluctuating/random readings and it would never be outputting a 0.7v reading, as it sometimes does? If anyone can offer some help, it would be greatly appreciated. Fingers crossed for a faulty sensor as it is a heck of a lot cheaper than a replacement cat!
I recently got a check engine light and a stored P2096 code, which according to my OBD2 scanner and Torque app relates to 'post catalyst fuel trim system too lean bank1'. I cleared the code, but it reappeared about 150 miles later. During a recent visit to Jasmine Porschalink for a seperate issue, I had them check the code on their Durametric and it showed the fault as 'Post catalyst 02 sensor bank 1, ageing'. I am not experiencing and loss of performance or poor idle issues. Fuel consumption has not changed.
In an effort to diagnose the faulty component I have been monitoring the pre and post cat O2 sensors using the graph displays on the Torque OBD2 app, but I need some help understanding the readings. As I understand it, the pre cat voltages should swing between around 0.2v - 0.8v per second (mine appear to do that just fine) and the post cat sensors should output a pretty steadyish 0.7v. Here is where one of mine seem a bit weird. With the engine fully warmed up, Bank 2 post cat sensor outputs a steady 0.7v at idle, but bank 1 is giving unusual outputs. Sometimes it will hold at 0.7v for a minute or two, but then it will seemingly follow the pre cat sensor (not identically, but the voltage swings up and down in a similar fashion). It will then suddenly drop to a steady 0.1v for a minute or two, and so on. These different outputs appear to be random and don't occur in a set order or for a set time. In short, the output is very unpredictable!
I understand that if the post cat sensor follows the pre cat sensor, it is a very good indicator that the cat has failed, but surely if my cat had failed I would not be getting such fluctuating/random readings and it would never be outputting a 0.7v reading, as it sometimes does? If anyone can offer some help, it would be greatly appreciated. Fingers crossed for a faulty sensor as it is a heck of a lot cheaper than a replacement cat!
