My SES is giving me code 0304 and 0503, bad KS and bad Left Front O2 sensor. First off, how much performance loss will each of these cause? It was my understanding that the bad KS will kill performance more than the O2S, and bad O2S will make for worse gas mileage.
Also, does anyone have a write up on how to replace the O2s? I couldnt find it on the HowTo fAQ.

 

the knock sensor will definitly make a big performance difference. your acceleration will be delayed.. like not alot of pick up.. becuz the timing is retarded.. so you should definitly get that fixed. it was a pain in th ***.. but once i got the knock sensor in.. and reset the ECU.. it was like.. dayam.. sooo much power was gained.. like.. the acceleration was kickin in.. felt dayam good. now for the O2 sensor. you need a special tool.. or you can use a wrench. using the special O2 sensor tool would be a better idea since it wont round out the O2 sensor.. not hard to do at all.. bigger pain in the *** is the knock sensor. get them both fixed.

 

is there a step by step somewhere on where to replace the O2?

 

you kind look around.. but if you want to replace an O2 sensor.. its not too hard. jus find the connector.. disconnect it.. then break loose the sensor from the exhaust pipe.. take it out.. and to install is reverse. shouldnt be too bad. maybe itll be hard to find hte connector for the rear O2 sensor.