Question on P0420 error code

I've had a 2010 that has been throwing the P0420 code. I haven't done much troubleshooting yet but one thing I've noticed is after sitting in the car for 10 minutes with the engine running I have a strong smell of gas or exhaust inside the cabin. Is this tied to the EGR system? I've looked at some posts but didn't see anything about a smell inside the car

SM-T970 ?

 

So it has 187,200 but the person who I got the car from replaced the engine in January with one from Japan JDM. From the 9,000 miles so far doesn't seem to be using oil from the changes I've done.

SM-T970 ?

 

I'm not sure what was done with the EGR but the previous engine failed due to a blown head gasket

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I was planning on taking it to the dealer next week if I couldn't figure it out before then.

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I've owned it since January and put 9,7000 miles. They did the engine swap right before I bought it

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So here's the latest update. I put it up on a lift and it appears to be leaking exhaust at the exhaust manifold gasket or the ring gasket right in the other end of the manifold going into the pipe.

The dealer quoted me $900 to replace the exhaust manifold gasket because Toyota recommends a lot of other parts to be replaced at the same time, multiple gaskets, screw posts, etc.

Since the engine was replaced right before I bought it I'm going to go cheaper for now and just replace the two gaskets at a local muffler shop this week. I'm pretty sure their three hours to replace both will be a bit cheaper.

Hopefully the code goes away after that

I've noticed the exhaust smell/leak only happens when the engine is cool and it's cooler outside. Once I've been on the freeway and driving a lot I can sit in a parking lot with the engine in and not smell anything. So I'm pretty sure it's a gasket issue.

SM-T970 ?

 

Sorry for the delay, so after having someone at an exhaust shop look at it for a couple of days, they found the leak was coming from one of the spark plugs. It wasn't tightened like it should so when it was cool it would leak out more and as it heated up it seemed to be more tight and not leak as much. Ihad them replace the spark plugs and coil and I haven't had any smells coming into the cabin.

I cleared the codes and after a week a saw my check engine light come on but I haven't checked to see if it is the same code. I hope to do that tomorrow.

I wouldn't have checked the spark plug after replacing the other gaskets but Iguess they have tools to help them find leaks.

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