Anyone else get P0421 code? It cleared by itself after a couple days, but not sure if the catalytic converters tend to fail or not? Just under 80k miles on my 2016.

 

not usually.

An exhaust gas leak can cause the issue, this is the first thing to check for.

Then check the sensors are working ok.

If these are all good then the cat will be faulty, but it seems premature for its age

 

Thank you, I’m taking it in tomorrow. My code reader shows the bank 1 sensor 1 usually above 2 volts. If I accelerate hard, it may drop below 1 bolt, but I’ve seen it get over 2 bolts as well. Car seems to drive ok though….performance wise.

 

Just got back, they monitored the rear O2 sensor then updated ECU software for rear O2 sensor. Covered under warranty and got a free car wash Hopefully no more engine light. Performance and gas mileage seem ok. I guess over 1 volt must be normal for the front O2. I think it might be a different type than the rear.

 

So it’s back on intermittently. Seems to occur mainly when it’s raining or possible may rain….

 

The flex pipe on the exhaust, at least on the V6, is prone to wearing through, I had a replacement welded in on mine. Someone upthread mentioned a leak could cause your issue, that would be the first place I would look.

 

Makes sense, very intermittent though, it seems as if it only comes on when it’s damp or raining. Did you notice any additional noise with the flex pipe leaking?

 

Yes, it sounded like an exhaust leak.

 

Ok, I need to do some additional maintenance soon. Next time I’m underneath, I’ll see if I can hear anything abnormally loud.

 

I'm having the same code p0421 on my Outlander. Did you figure out what was wrong with yours?