ok...2007 plain impreza 5 speed

 

was getting the infamous P420

finally got around to doing to O2 cheater as state inspection is due 6/1

 

used one screw in cheater...cleared codes and these codes showed up:

P1518 subaru specific

P442--Evap sys. "small" leak

P456--Evap sys "very small" leak

P420

 

Added a second cheater (worked like a charm in my 96 OB) and I am still

getting returning codes that wont go away

 

Now it is

P2096 post catalytic fuel trim sys too lean bank 1

Pending code: P1037 o2s ckt low volts 1 2

 

any help would be greatly appreciated...?

I am afraid that 2005+ models are too smart for the cheaters.

I have an intermittent P0420. After reading about all of the possible real fixes, costs and potential lack of solution, I bought a small code reader for about $20 on eBay (Autel MS300). Clear the codes, drive a few cycles at various speeds to get all systems "ready", rescan to make sure no codes and no codes pending and then run to emission testing center.

Since my code is intermittent, I justify this method as "coinciding" the timing of when the code is present or not with my visit to testing center.

hopefully someone has some other suggestions....mine won't go away with repeated clearing

i am wondering if anyone has tried changing both 02 sensors with any success

and what about after moarket vs. OEM

My has 3 cats and 5 sensors! 2 precat, 2 post cat and one on top of rear cat after the two join.

I spoke with Bosch tech support after replacing the front precat with OEM and while it would seem in his interest for me to buy his sensor for the rear, he suggested it wouldn't help.

Just my experience and not meant to dissuade or mislead.

The newer cars use an "Air flow ratio" sensor not an O2. They use 02s behind the cats usually but a/f ratio's in front for more accurate management. They run off a 2-5v referrence instead of 0.0-0.9v. They run off dual frequencies also so theyre harder to trick.

I am afraid that 2005+ models are too smart for the cheaters.

I have an intermittent P0420. After reading about all of the possible real fixes, costs and potential lack of solution, I bought a small code reader for about $20 on eBay (Autel MS300). Clear the codes, drive a few cycles at various speeds to get all systems "ready", rescan to make sure no codes and no codes pending and then run to emission testing center.

Since my code is intermittent, I justify this method as "coinciding" the timing of when the code is present or not with my visit to testing center.

 

Ecco this. I get that code about twice per year. I just make sure I get my inspection when that code is at bay.

replacing the O2 sensors and making sure you don't have any exhaust leaks can make the codes go away. i don't know if that's a %1 success rate or %95 success rate though.

 

i think for 0420 code you would replace the rear ones first...but that's just a guess.

Rear ones are a lot cheaper and I've had success replacing them on early 00's cars to cure a 420 code. I haven't had the opportunity on 05+'s.

 

The pre-cat A/F sensors cost twice as much and they stay pretty accurate. They are Air/Fuel ratio sensors, not airflow. The output is also read in current rather than voltage by the computer, but that's quibbling.