I believe I need to replace the O2 sensor after the catalytic converter. I was having trouble codes indicating a miss match between the pre cat sensor and the post cat sensor. I removed and cleaned both sensors and they worked fine for a few months. Both sensors were slightly loose fitting and seemed to report trouble during wet periods. I think I had a grounding problem. Now I am getting P0420 -Catalyst efficiency below threshold- indicating a bad sensor after the cat or a bad cat. I would prefer to change the sensor considering my previous troubles. (I wish I could remember the previous code). The dealer part is about $160. I ordered an OEM part from Autozone $69 and ended up with a three wire unit with a triangular plug Bosch #13036. The original is a 4 wire unit with a rectangular plug. They have a 4 wire unit Bosch #13469 that their book indicates is for the pre cat sensor. My pre cat sensor has 5 wires. Does anyone know what part I can use for this. I can solder in a generic but I want to make sure the unit is a match before I go to that much effort. Also, I would not mind paying a little more for an OEM easy plug in install, but I would like to find one from an auto parts store instead of paying the stiff bill from the Subaru Dealership.

Try www.subarugenuineparts.com They are a subaru dealership that sells parts online. They are the cheapest online dealer I have dealt with (and always cheaper then your local subaru dealer)....and I've used about 4 or 5 of them now.

there is a 4 wire o2 sensor out there, ireplaced mine afew months back but i can't remember where i got it but i will look for you.

 

my code was also said cat below threshold and i replaced the cat with a good used one and replaced the sensor also and no codes anymore.

 

i will search for the web site i got the 4 wire sensor and let you know.

DanO

try oxygensensors.com, they have afew 4 wire downstream depending on your vehicle. i used the universal, connected the wires accordingly and it worked fine.

good luck.

DanO