P0421 code

[littlemoule]

Closing this off by saying the only viable option is a direct fit converter. Shop confirmed it. Secondary converter is not monitored. Planning to drive this as is for a bit as have developed a new issue which is more urgent with the transmission. With that, closing this off. Conclusion: For mirage, you are better off with direct fit converter because of a 90 degree tilt the converter has.

[Fummins]

Too bad, just 20k kms past getting a free cat from Mitsu.

And...there are aftermarket direct-fit cats available.

[littlemoule]

Precisely, this part will do the job but since it is about $400 CAD + tax and am dealing with a new clutch job soon, this will have to wait. Atleast there are parts available. Just for other people don't expect to put in a $150 cat because it wont fit the mirage.

[7milesout]

It looks too long and skinny to fit where the first cat goes. I don't know, but I think you'd need one more fat n stubby.

Hmmmmmmm.

[Fummins]

I'm sure someone could make a $150 cat work but then charge $250 labor. ... I have a few old 15' cats laying around and could probably walk 100' and grab a universal cat off the shelf....Hold my beer.

Edit: I remember someone on the forum using some magic potion that was suppossed to clean the catalytic convertor. I thought it was snake oil but they claimed it works. I can't remember who it was but I think it was someone from Europe or somewhere they have emissions testing? Might be worth looking into. I'm sure it was some stuff you dumped in the gas tank. I'll look and post back if I find it.

I give up, can't find that thread/post.

I can't remember if op ever did end up replacing spark plugs or not but I'd give that a try before replacing the cat. I had a pissed off customer with an oil burning turbo cruze that went through that p0420 or p0421 codes. Replaced the cat and the same code came back in under a week.

Some of these codes will take days/multiple drive cycles to show up as a trouble code. For example, I unhooked my charcoal canister and drove for a few days before the cel actually came on. The great part about driving with your Cel on is that if I do have another code appear you don't have to stress about it cause you won't know unless you scan it. It's a win win. If you do sell the car just use the hilariously over-used line: "it's an O2 sensor code" lol

[Navysteveo87]

Ok I'm back. Sorry for posting on an old thread (almost a year old) but I'm having the same issue as littlemoule had to a T. (Cylinder 1 was misfiring (for 2 weeks) and dumping fuel in the cylinder that wasn't getting consumed, it's possible the raw fuel being pushed into the catalyst could have degraded the efficiency/lifespan of the catalyst)

After Johnny Mullet fixed my corroded wiring harness back in February the car has been running great but the mpg's are now suffering (was getting 37-40 mpg highway prior) and now the CEL (P0421) has been on since

https://mirageforum.com/forum/showth...ctrical-Issues


I've tried the old Scotty Kilmer lacquer thinner in the gas tank trick to clean the cat but that did nothing.

https://www.youtube.com/watch?v=5icT...eSBraWxtZXI%3D

I just purchased O2 sensor spacer/defoulers to try and trick the computer into turning off the CEL. Has that worked for anyone before or should I just remove the front cat and clean it with soap/water?

https://www.walmart.com/ip/2Pcs-O2-S...ole/1093527612

Also, How many O2 sensor's does the 2015 mirage have, two or three? Thanks

[Fummins]

Ok I'm back. Sorry for posting on an old thread (almost a year old) but I'm having the same issue as littlemoule had to a T. (Cylinder 1 was misfiring (for 2 weeks) and dumping fuel in the cylinder that wasn't getting consumed, it's possible the raw fuel being pushed into the catalyst could have degraded the efficiency/lifespan of the catalyst)

After Johnny Mullet fixed my corroded wiring harness back in February the car has been running great but the mpg's are now suffering (was getting 37-40 mpg highway prior) and now the CEL (P0421) has been on since

https://mirageforum.com/forum/showth...ctrical-Issues


I've tried the old Scotty Kilmer lacquer thinner in the gas tank trick to clean the cat but that did nothing.

https://www.youtube.com/watch?v=5icT...eSBraWxtZXI%3D

I just purchased O2 sensor spacer/defoulers to try and trick the computer into turning off the CEL. Has that worked for anyone before or should I just remove the front cat and clean it with soap/water?

https://www.walmart.com/ip/2Pcs-O2-S...ole/1093527612

Also, How many O2 sensor's does the 2015 mirage have, two or three? Thanks

They have 2 sensors. The front one affects how it runs and the rear one just monitors to crap coming out after the cat. If the two readings are too similar the. It cry’s and throws a cat efficiency code. I don’t believe the rearO2 sensor affects fuel economy

[Navysteveo87]

At 1:15 this shows two sensors in the engine bay

https://www.youtube.com/watch?v=0NM55ar7GSE

Isn't there a third O2 sensor under the car where the cat & muffler are located as well?

[Fummins]

At 1:15 this shows two sensors in the engine bay

https://www.youtube.com/watch?v=0NM55ar7GSE

Isn't there a third O2 sensor under the car where the cat & muffler are located as well?

No that video shows 2 sensors. The front one on the exhaust manifold and the second one is further down behind/after the front cat. It looks much closer than it really is in the video because he zooms in on it. That car in the video isn’t from North America but the sensors are in the same spots

[Navysteveo87]

Yeah I get that there are two o2 sensors in engine bay but I'm pretty sure there is another (third) o2 sensor under the car AFTER the second cat. This is a US mirage so there might be extra emission controls versus your Canadian version