Ok, just got the '13 Outlander Sport out of the shop ($334 to replace the tailgate latch to get the door working from the outside again BTW) and 2 days after that repair on a 3 hour road trip my service engine soon light comes on. After going to Advance Auto to use their scan tool, the only code that comes up is P0420 - Catalyst System Efficiency Below Threshold Bank 1. According to a couple of sites, could be:
-Three way catalyst converter Bank 1
-Exhaust tube
- Intake air leaks
-Fuel injectors may be faulty
-Fuel injector leaks
-Spark plugs may be faulty
-Improper ignition timing
-Engine Control Module (ECM)

I have the ability to check and replace the plugs but that's about it given my tools and no garage. Anyone have experience with this code and any guesses as to what it likely could be? If its O2 sensor the price could be upwards of $1100 and I only have $7K left on it.

 

I have a 2010 Mitsubishi Outlander GT. My Outlander has 153K miles, and it recently withing the past year been spitting out that code. I have bought cata-clean at autozone at least three times. It makes the code go away for about three months. Let me know what you end up doing to fix your problem, or if you have any suggestions for me, since I am dealing with the same issue.

 

Buy an O2-sensor extender. This worked for many people. Once installed it places the sensor further away from the flow and apparently fools the ECU. The item is something like this:
Oxygen sensor extender

 

Thanks man.