My car is 2003 Mitsubishi Lancer ES, and engine service light is on, code is P0421.

Dealer told me to replace exhaust manifold with Catalytic Converter .
and universal converter

what is universal converter?

somebody says that maybe problems are Oxygen sensors.

How can I identify which one is upstream or downstream? Thanks.
Is it esay to replace them if I wanna do it by myself ?

if replacing exhaust manifold with Catalytic Converter, can i do it by myself? is it easy?

Thanks a lot.

Kkf

 

I just got your PM.

First off, if you have more than 100k on the car, then the catalytic converter could very well be the culprit, as could the o2 sensor.

The best way to tell is to pull the o2 sensor and inspect it visually. If you see it covered in carbon, yeah more than likely that's what the problem is. The upstream sensor is the one you'd be looking at, and you can identify it easily because it's the closest to the engine (before the catalytic converter).

Don't pay dealership prices either, you can do it yourself with just a wrench and a little time. The cat is equally as easy to replace.

 

I believe part #40567 is the correct one in this case (the eBay link). I'm fairly sure the car has two catalytic converters, one on the exhaust manifold and one somewhere else down the exhaust. That is the 'rear unit' (#40524) you speak of.

The dealer is also telling you to replace both of them from what I can tell. In my opinion, if you aren't throwing a code for that particular one, it doesn't need to be replaced. That's just to rack up a bill. (I don't want to hear it Manybrews, dealerships do it all the time lol) If you can turn a wrench, you can do this in a single day fairly easily. I have done it on other cars, and the longest one took me was 4 hours because I broke a bolt.

The catalytic converter is designed to last about 100k miles, at that time it will most likely break apart. From what I remember there was also a recall on the catalytic converter for this car, which you should have been notified about. You just might be able to get them to cover it if you play your cards right. Most people just throw the notices away because they think it's junk mail. That said, the emissions system warranty is 100k miles, and because your car is over that they will likely tell you to bark up a tree.

I would certainly get it done as soon as you can since it can cause a massive problem with it being so close to the engine, the likelihood of fragments being sucked into the engine is decent in my opinion. Some Nissans are notorious for it, not so much Mitsubishi.

EDIT: The more I read the more it sounds like catalytic converter failure. You could pull the o2 sensor and check its condition, but I doubt that's the cause of the P0421 code.

 

No you don't have to drain the oil. You aren't doing any internal engine work, so you're good to go.

Just make sure you don't hit any air conditioning lines. The thing that helps me the most are a set of ramps from autozone that you can drive the car up, and then you can easily get under it as needed. Make sure you have loctite so no bolts back out on you. Some people like to tighten the bolts after a couple weeks just to make sure.

Most importantly don't forget the 6pack, that'll come in handy

Have fun! This should all be nuts and bolts, just keep track of everything.

 

We have a 2003 Lancer ex and the engine lite keeps coming on. My daughter went to autozone and then said it was coming up with code P0421. My daughter took the car to a dealer and they said it would cost a $1000 to fix and the catalytic converter which needed to be replaced was like 500-700 dollars. Also her compressor for ac is shot and was told that was going to cost another 500. Is this something easy to fix yourself and what are the costs? I checked online and found this one place called rockauto and the converters were under 100. Any help in this would be greatly appreciated.

Desperate mom

 

Desperate mom, if you read what I wrote just a few posts above, it should answer all your questions.

 

The P0421 code is for the driver side, or first from the engine (depending on the configuration on the engine), catalytic converter. The O2 Sensor sometimes is the reason, but more so than not, it's the converter.
Kkf, when you got your prices from the dealer they gave you the direct fit (bolt on) converter price and the universal (can fit on any car) converter price. Direct fit is easier to work on, but more expensive. If you have little automotive knowledge, but are willing to learn, go that route. The universal one will require you to cut, clamp, and possibly weld the new catalytic converter onto the existing pipe.
Average costs: Direct fit $150-$300 with install $250-$500
Universal fit $50-$150 with install $400-$700
Desperate Mom, as just stated the catalytic converter can be easy to fix. Do NOT try to replace your AC compressor by yourself if you want to keep your warranty on the parts. Most compressors have a 1-2 year warranty with replacement of related parts. You will have to replace the orifice tube/expansion valve and the receiver/dryer. Also you must get the AC system professionally flushed.
Average costs: $400-$1000 (with related parts) with install $700-$2000

 

Please refrain from giving advice if you aren't 100% sure of what you're talking about. The primary catalytic converter on this car is on the header itself. How would you suggest someone cut and weld that? You must replace the entire unit.

Warranties are a load of **** too.

 

Then why did the dealer give the option for a universal one? On most cars, the front pipe can be cut and modified to accomodate a universal converter. In this case though, an aftermarket header is required if you want to put on the universal one, which still requires cutting, clamping, and/or welding.
Maybe for you the warranties are ****, but to the person who can not afford to have the same job done twice, they mean a lot. Sometimes the peace of mind alone of having a warranty in place is enough.

 

I've had the same P0421 for the past year and I'm getting around to finally fixing the thing. My question is one of clarifying what needs to be replaced. Of the two cats, which one should be replaced with this code, assuming it's not the O2 sensor? The sickeningly pricey front unit or the rear? Or is there a way to tell for sure?
I guess the OPs post where the dealer said "manifold" is a hint that it's the front unit?

As far as which O2 sensor is involved with this code, I thought it's the downstream sensor that's sending the fault, no? Then again, I guess it could be either or both that's actually bad.
http://www.obd-codes.com/p0421