B_Swapped93

It's a TSX but pls don't move this. Bone stock auto coming up on 101K miles I got p0420 today i'm assuming this is my #1 o2. I have no problem going to Honda and getting them to do it, I just want to know what happened to my car.

B serious

iTrader: (1)

Its a catalyst code. Not an O2 code. And the primary O2 is not in the catalyst.

Your cat is no longer working as well as it should.

The secondary O2 is working because it realizes that the cat is below threshold.

So...you probably need a cat. If you go to honda, this will be like a $1k bill.

Or buy a used OEM cat on ebay for $200 and slap it on.

**edit: honda extended their emissions systems warranties. So you may be able to get them to warranty this. If your car is not modified and the cat has not been damaged by you running over something, and if the heat shield is still present.

t3h jam

spark plug non-fowler / o2 spacer installed between the exhaust bung and the rear o2... save yourself a few $$ and buy a few years.

B_Swapped93

Was worried it was the CAT, should have mentioned it was a magna-flow one unknown km's too for the price of those it's cheaper than the 1K+ OEM one.

will this kill my mpg? it takes a while to get stuff I order where I live/shop to take the car in there's one exhaust shop I trust in town.


thanks

B serious

iTrader: (1)

Nah, it won't affect mileage. Unless the cat is physically broken or clogged inside.

You can run an O2 defouler (fooler). High flow cats and aftermarket cats usually require the secondary O2 to wear a defouler to cheat the O2 to tell the ECU that everything is OK.

vshavoc

Just throwing parts on it is pointless. I always say diagnose the problem. I've seen P0420 codes for bad sensors, cats, and engine combustion inefficiency problems caused by other bad sensors, misfires caused by bad ignition parts, and I've even seen those codes because of valve adjustments being off but it should misfire on the misfire counter or even throw a misfire code. The cat is monitored by the rear O2 sensor. The front A/F sensor is controlling fuel trim in closed loop. Now if the A/F sensor fails the ecm will adjust fuel trim off the rear oxygen sensor to protect the cat but other than that, the rear oxygen sensor just monitors the cat. If you looked at the signals for the front and rear sensors in global mode on a Modis, the front should be switching fast and the rear should be switching slow. I say global obd because if you're in manufacture specific it will show different waveforms because it's an A/F sensor on the tsx. Global should convert it to 0-1 volt like regular o2's. Anyways if they are both switching at the same time, either the cat is bad or the engine isn't running efficient. You could test the sensors by injecting propane and creating a vacuum leak to make the sensor peg each way while scoping it. The switch time should be quick. They say 100 milliseconds but if it's slower than 50 milliseconds it's lazy. They should also go over 850 millilivolts and below 150 millivolts. You could google this stuff. If the sensor switches fine then those are good. If your fuel trim is more than + or - 10% then you have an issue and need to tackle that. But usually you just drill a hole in front of the cat and use the tailpipe to test after the cat. Use a 5 gas analyzer and run the car on the dyno and take emissions readings from in front of and behind the cat. Google a catalyst efficiency calculator and check to see if the engine readings before the cat are efficient. And I mean high 90% efficient on newer cars. If it isn't start troubleshooting that. Now enter the numbers from out of the tailpipe and it will tell you how efficient the cat is running. I think it should be over like 70-80%. I can't remember exact number on that. If it isn't, then you know for sure the cat is bad. You could also use an infrared gun and check the heat going into the cat and out of the cat. It should be much higher temperature coming out than going into the cat. They'll rattle too if they are coming apart and you tap it with a mallet. You could also run it at 2500 rpms with the sniffer in the tailpipe for a little bit and then snap the throttle. If your oxygen goes up, that's telling you the cat isn't oxidizing anything nor storing oxygen for later use. I can go on and on, but that's why you pay for a diagnostic. Throwing parts at cars is silly. I'm a ASE smog and repair tech btw.

B serious

iTrader: (1)

^You're correct.

But in his situation, its almost surely a cat.

He could pay $200 or so to scope it and have it tested, etc....and then buy parts. Unless...you know someone who rents scopes and trains the renter on how to use them.

Or $200 to buy the most likely culprit and fix the issue at the same time.

A cheaper test (if you were into testing) would be to install a defouler on the rear O2 sensor. If the CEL goes away in a week or two...that would tell you that your cat is bad.

B_Swapped93

can I get a defouler at a part store etc? i'm not driving it much just cause I need my suv for now.

B serious

iTrader: (1)

You can make a defouler from a spark plug defouler at a parts store.

Or buy a more effective 90 degree defouler for like $20 on amazon or at a performance shop.

Either should work on a 04-05 TSX. The 90 degree is more likely to isolate the secondary O2 from the exhaust stream.

You're basically showing the O2 sensor the amount of oxygen it needs to set a "flat" signal. If it sends a flat signal when its shown more oxygen...it tells you that the O2 works...and the cat is under efficiency.

EnjoyTheRideDC2

iTrader: (1)

Looks like your P0139 issue you had months back wasn't the result of an o2 sensor problem....

Makes you wonder why a catalytic converter needed replacement in the first place. The previous owner must not have taken the car to get serviced @ the dealership and the shop that he did go to didn't know about the emissions warranty. Otherwise, there wouldn't be a magnaflow cat welded in place.

This would be the second time the catalytic converter would need to be replaced. The previous owner was probably advised to do the same after similar diagnosis from a shop. These things aren't meant to be replaced on bone stock TSX's. If the catalytic converter is toast, replacing it may only solve the problem for the short term. What you may be experiencing is a fuel issue, running either too rich or too lean. It may even be an exhaust leak that's causing your o2 readings to be off and causing the ecu to adjust fuel trim incorrectly. Running lean/rich will destroy the catalytic converter prematurely.

Is this the only code you're getting when connected to the reader? Or are there additional codes besides the p0420?

What did your rear o2 sensor look like when you replaced it last? Do you still have it in your posession?

B_Swapped93

p0420 is the only code. That other one went away after the OEM sensor was put in, no I don't I had to take it to the dealer they would have trashed it. i'll try re-setting it and see maybe it comes and goes

B serious

iTrader: (1)

The original cat may have been replaced due to an impact or some other reason than failure.

Does Canada still use MTBE in their fuels? Idk how quickly that kills cats.

The magnaflow cat was doomed from the start. We all know how well Hondas do with aftermarket universal emissions components.

EnjoyTheRideDC2

iTrader: (1)

Impact? It's not easy for something to make contact and damage a cat on a TSX while driving. Probably even tougher to do so while parked.

EnjoyTheRideDC2

iTrader: (1)

Why not just have those techs you know at the dealer do another free diagnostic for you? Maybe they can help determine whats causing your CEL to go off...

B serious

iTrader: (1)

I am currently working on a TSX that has a broken catalyst. From impact. What do you mean "while parked"?

He said that the PO replaced the original cat. Maybe the PO smashed into a rock in the road...a curb...a sasquatch...whatever. The cat is one of the lowest hanging parts of a TSX.

Finding out WHY the cat went bad is important. However...the original cat could have gone bad due to lots of things. The magnaflow cat was never going to work for more than a year or so anyway.

Feel me what I'm sayin? Boy-eeee

B serious

iTrader: (1)

If the car was killing cats due to an over-richness or misfire...then a CEL for those things would have turned on LONG before the cat went bad. The CEL is there solely for emissions reasons. The parameters are set conservatively enough to preserve the cat's integrity.

The cat can handle more punishment than the ECU will allow it to endure. If the car was running rich enough that the computer thought there was any chance the cat may be damaged...it would turn on a CEL.

Or test it for long term fuel trim. That might tell you something...maybe...maybe not.

B serious

iTrader: (1)

BTW I'm not undermining anyone's suggestions. You're all correct. I'm just talking through the most likely scenarios in the ways that I have experienced them.

Mad respekt.

EnjoyTheRideDC2

iTrader: (1)

There are different ways a catalytic converter can fail, but aside from a manufacturer defect most of them are engine related. Catalytic failure due to contact isn't a common issue amongst TSX owners. The fact you're supposedly working on one that has doesn't justify much. This sounds more widely accepted:

Catalytic Converter Failure At 43,000 miles? - AcuraZine Community

Catalytic Converter / O2 Sensor Malfunction...Confused! - Acura TSX Forum

I agree, finding out WHY the cat failed in the first place is important. But I dont see anyone trying to diagnose the issue at all. Your suggestion was to skip diagnostics and swap out the part that most likely failed.

The OP just had a rear o2 sensor replaced not long ago. Now a CEL pops up for catalytic converter inefficiency. No one even knows at this point if the cat is even bad. We are all under the assumption that the current cat was installed correctly or was even suitable for the application.

Magnaflow converters aren't junk nor are they built to only last 12 months before needing to be replaced. They still carry an 8yr/80k mi warranty just like the OEM original part. If the Magnaflow replacement fails, its probably for the same reason the original one failed for in the first place and was never addressed/repaired.

B serious

iTrader: (1)

Lol. I like the comment that I am *supposedly* working on a TSX with a broken catalyst. Yeah...I only said I was to impress you and to make you believe me because that's the most important thing in my world.

I also don't know the OP's history of failed O2 sensors. You seem to be paying attention, though.

I also suggested using a defouler to test the O2 function.

Those were my suggestions. Based on experiences that I *supposedly* have.


I never claimed that impact was a common type of failure on any car. I suggested it as a possible cause, stating "we don't know why the PO replaced the original".

But...your posts did jog my memory about 04-05 models having cats that failed prematurely, which I believe prompted Honda to extend warranties. Maybe the PO didn't know this.

FWIW, my 06 has the original one at 135k miles. I believe they improved the design in 06?

Good luck, OP!

B_Swapped93

So with said defouler will that make it temporally subside the MIL, I drove it a few days last week it was off. Now its back I've been on the fence on selling this car to fund something else... so how can I temporally make this go away. I'm not trying to cheat anyone those magnaflows are $100 I just don't have the time anymore to deal with this. So just go to the part store and get a plug defouler and drill it out?

EnjoyTheRideDC2

iTrader: (1)

Is the current catalytic converter straight welded onto the exhaust piping or is it flanged and bolted in like stock? It's really hard to suggest a solution without knowing more about or seeing what we're dealing with here. It could be anything from an exhaust leak, running bad quality gas, fuel/ingition system issue...

Replacing the cat will usually get rid of the CEL. That should last long enough to sell the car, if thats what you plan on doing.

B_Swapped93

it's welded into a flanged section but the bolts wouldn't come loose without oxy/acy and I don't have those gases. It was fine all this time before I changed nothing i'm not looking to shell out more for welding a new one in just a 24 hour fix per say, its bone stock too.

EnjoyTheRideDC2

iTrader: (1)

It's an assumption that the cat was fine all this time. The failing cat could've caused your o2 sensor to foul up and throw the p0139 code you initially dealt with. First response to your post...

https://honda-tech.com/acura-tsx-46/...x-off-3245051/

When you had the o2 sensor changed out, nothing was mentioned to you about the cat? For all you know, maybe your o2 sensor was fine the whole time and the reason for the delay in signal was a failing cat. Maybe the previous owner had the same idea you're having about selling the car due to the ongoing issue you dont want to deal with? So he welded on a cheap cat and handed you the keys.

Is this cat welded into the factory location? You say its welded into a flanged section. Considering the size of the OEM cat, it isn't hard to find a direct bolt in replacement that would require no welding.

You have to make the choice : Swap out the cat and sell the car or determine the actual issue with the car and repair (which might include replacing the cat). You can spend the time trying to use a fouler, but considering you couldn't remove your o2 sensor previously, I'm not sure it would be easier the second time around. Not to mention, the fouler may not cure the issue and waste your time.

B_Swapped93

Despite what you think it's seriously hard to find used tsx stuff and with our dollar being .25 under the USD ebay isn't really an option. If I could unbolt it and bring it to them like that I would, i'm not looking to drop another 200+ in if it prevents me from getting the price I want maybe then I'll get another magna-flow one. i'd just likr a quick 24hr fix persay.

EnjoyTheRideDC2

iTrader: (1)

Who said anything about used TSX parts?

I'm not sure what you're referring to when you say: There's no 24 hour fix for this issue and its tough to diagnose anything without knowing more about the car. It doesn't seem like you want to spend much time going over the car to check for exhaust leaks, faulty ignition parts, or test sensors for functionality. Not sure if it's because you lack time, resources, or you dont have the desire to work on this car.

This is the cheapest advice I can possibly give you: As mentioned by B serious, Grab a spark plug fouler, drill it out, place it in the secondary o2 sensor location along with the o2 sensor itself. Grab a bottle of a good quality fuel system cleaner. Pour it in and fill up the car with the highest grade fuel possible. Reset your code and see if that will remedy the issue. If it does, pour nothing less than premium grade fuel until the car is sold. This should cost you no more than 30CAD out of your pocket. If it doesn't work, you're only out the cost of the fuel system cleaner plus the 2-3 bucks more you paid for premium gasoline.