Need help identifying problem
I am getting some fault codes that I don't understand for my 1994 850 turbo. First, some history. Over the last 3 years, about every 2-3 months I got a 1-4-3 (knock sensor) code. Some of the information I read stated that the knock sensor seldom goes bad and that it can be related to vac. leaks. I did find one hose off and then last fall got codes 443, 143, 435 (?, knock sensor, O2 sensor). I replaced the front O2 sensor with a bosch universal that I carefully soldered the leads on and used shrink tape. It wasn't very long before the check engine light came on. I was sure it would be the knock sensor again but it wasn't. I'm now getting codes 436, 435, 212, 153 (?, O2 sensor, O2, ?). I should also mention that when the check engine light comes on, it seems to have very little effect on engine performance. I may drop a mile per gallon on gas mileage but even that may be coincidental.
As you can see some of these fault codes are not even listed in the code table. Should I have replaced the rear O2 sensor as well? Did I make a mistake using the universal Bosch sensor? What are these codes that aren't listed on the table? If I do need to try replacing the O2 sensor, should I try using Sea Foam first. Thanks for any help you can provide.