Peake Fault Code Oxygen Sensors
 

Maybe someone could help me out, I got a 2003 4.4i E53 w/78,000 miles. I got SES light and i used Peake tool and got 0F - 0E -10.

So I went to Table 0F and went to 0E Code and it reads Aftercat 02 sensor cyl #1-4 and code 10 reads Precat 02 sensor aging cyl #1-4, does this mean that both pre and post cat 02 sensors need to be replaced and this is on the passenger side underbody? Not 100% sure where cyl. #1-4 are. I am not sure if both or just one 02 sensor needs replacement is aging means its okay, and also should i replace the other side in pairs as well? I read you should replace Pre's in pairs and Post in pairs, since I got one of each in the fault code I should replace all 4?
Thanks, in advance.

It's odd that you're getting post-cat errors. It's the pre-cats that read the 02 in your exhaust, then they feed the ECU to adjust fueling. The post-cats are simply there to confirm that you've got cats actually installed on the vehicle and do nothing for tuning, running issues, etc. I got my replacement 02's from Autozone for around $70 each. As much as you may not want to, I'd suggest replacing both pre-cat 02's (it'll help gas mileage in the long run), reset the codes, and go from there.

It's very common on the 5 and 7 boards that people have replaced cats around the 100k mark, so I'm still waiting to see those same issues start coming up around here as the X5 ages.

Well I ordered a Post Cat O2 already, so I guess I will just get two new precats, reset code and see if SES light comes on, If it does then i will also replace the post cat one, I had adv. auto parts scan with the actron and it said 02 heater malfunction bank 1 sensor 2, i know sensor 2 is post, but it had another code which now with the peake seems to be the same side precat. The truck does seem sluggish after reaching operating temperature, going from 2nd to third gear, it drags a bit as it revs from 2-3K RPM mark, in the morning it zips up quickly at cold start. I plan on also replacing spark plugs NGK i bought and Fuel Filter which i also bought already, just trying to take care of one thing at a time and SES light is annoying!

For the aging faults you simply need to replace the O2 sensor affected by the fault. For the post cat O2 fault, there are only two kinds of faults for post cat O2 sensors... catalyst efficiency faults which indicate the cat converter isn't doing its job properly and the same aging fault which just needs the sensor.