hey i drive a 2000 impreza rs 2.5 liter, a while ago my check engine light came on and i didn't check it till recently when i needed emissions to be passed. Turns out i had a bad 02 sensor and a code PO420 was set (system catalyst effieciency low front bank) well i replaced the 02 sensor hoping it would clear the other code also but it didn't. My check engine light came back on and now its just the PO420. My question is does this mean since it took me so long to replace the front 02 sensor that it fried the front catalytic converter? does just disconnecting the battery for about 20 minutes reset the computer?? the converter is 480$ i need to know because i don't want to drop this kind of coin and have it not work still. Maybe if i replace the 2nd 02 sensor it would fix it i don't know. Please respond quickly thanks!

 

If you can do a cat efficiency test on the car. Did you clear the codes after you pulled them, cause if you don't then it will pull it again. The O2 sensor if left in will not fry the cat. Do the test and clear all codes. That is really the only way to find out

 

how do i do a cat effeicency test? i don't work in a shop i got autozone to pull the code for me, and does disconnecting the battery clear the codes?? or do i have to get autozone to hook their little scan tool up to clear the code

 

Ask autozone to clear the codes, and if they do the lights shouldn't come back on if all is good. To do a cat effeicency test you need to go to a shop. Disconnecting the battery won't clear the codes on most newer cars.

 

1- be sure you have you fav. fuel in the tank and have run it for 40-50 miles after fill up to make sure the grades / brands are changed
2- disconnect the ( - ) negative battery terinal and let car sit for 1 hour
3- reconnect battery, and start you car(DONT EVEN THINK OF TOUCHING THE GAS TO START) let start all by it self
4- let idel for at least 20 min. to set new air/fuel ratio
5- trun car off then restart and go for hard drive bounce off redline in 1st and 2nd gear, after that wide mix of driving style (fast ,slow,city, highway)
6- over the next few weeks the ecu will continue to learn and a immediate drop in gass milage (city) is temporary and will improve to normal.

also subaru recalled the 2000 rs 2.5 to be reprogramed cuz the range for the check light was to narrow and the light was comming on and nothing was wrong with the cars.. so check with your dealer for the recall..

suberacer@hotmail.com

the ecu reset is from is from a good friend Larry Ganz http://www.imprezars.com/images/installganzflow.pdf