OK, the heating circuit has failed on my downstream O2 sensor(CEL code P0141). As I understand it, this sensor does not affect fuel trim but only monitors exhaust. My Subaru still runs fine with a very slight decrease in MPG. Dealer wants over $300 to replace and says if the sensor is not replaced, …

Rear or downstream O2 sensor

oldschool May 1, 2009, 5:09am 4

With this code set you will be running in open loop regardless of the reason the code is set. Constant open loop operation can’t be good for the cat.