My ECU threw P0420, so I searched the forums and found this: Oxygen sensors/Check engine light which describes how to install a non-fouler. But when I crawl under the Outlander, all I see is what looks like an O2 sensor before the cat, and directly on the cat, but none after it. From what I understand, the non-fouler goes on the sensor "downsteam," but in all other cases I've read that meant a sensor placed after the cat. For the Outlander, does anyone know if I should place the non-fouler on the sensor connected directly on the cat? Thanks!

 

Why do you want to install a nonfouler? Maybe just replacing the O2 sensor will solve the problem. On a 2011, you should not have a failure of the catalytic converter and if it is, you should be covered under warranty for emissions items. P0420 can be caused by many issues, for example:

• Leaded fuel was used where unleaded was called for
• A damaged or failed oxygen sensor (HO2S)
• Downstream oxygen sensor (HO2S) wiring damaged or connected improperly
• The engine coolant temperature sensor is not working properly
• Damaged or leaking exhaust manifold / catalytic converter / muffler / exhaust pipe
• Retarded spark timing
• The oxygen sensors in front and behind the converter are reporting too similar of readings
• Leaking fuel injector or high fuel pressure
• Cylinder misfire
• Oil contamination

You might want to start investigating why the code is being throwm instead of just trying to mask it by installing the nonfouler. The problem causing the code will still be there.

 

(Thanks for your reply, and I apologize for my late response)

I wanted to install a non-fouler because the instances of the fault code are irregular, and only appear to be triggered by a change in weather. For example, P0420 will show early in the morning when there was a rapid change in temperature overnight from hot to cold, and disappear within an hour of driving and the engine warming up. I've seen this code appear and disappear once or twice within a week, then be absent for several months.

I thought that if I could alleviate this problem with a non-fouler at $5, then I should give that a shot.

Does the code appearing during a change in temperature indicate any of the other symptoms you described?

Thanks!