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P0420 Code: Oxygen Sensor or Catalytic Convertor?

168K views 26 replies 14 participants last post by  forbes_n 
#1 ·
Hi all,

My 2009 started tripping a P0420 code yesterday and the manual says it's described as a "Catalyst System Efficiency Below Threshhold (Bank 1)" issue.

I heard that it was either a bad oxygen sensor or a catalytic convertor that needed replacing. I'm right about 60,000 miles, so not sure if it would be the catalytic convertor; do they normally go out that early? Either way, does anyone recommend a good method to test for either of these that doesn't cost an arm and a leg? Perhaps something DIY? Please advise!

Thanks,

Izz
 
#6 ·
I must admit, I've not bought an O2 sensor in many years, but the last one I got was from a local auto parts wholesaler and it cost me $25. They should never cost over $50. Anything more is just highway robbery. Eh?

:cool:

Edit: Here is the Advance Auto Parts O2 Sensor.
Buy Denso Oxygen Sensor Direct Fit 234-4165 at Advance Auto Parts

As I said, "Highway Robbery!"

On the other forum, this topic went on for days, and some guys found inexpensive O2 Replacement sensors. Maybe Jeff or Larry knows of a cheap replacement.
 
#12 ·
I must admit, I've not bought an O2 sensor in many years, but the last one I got was from a local auto parts wholesaler and it cost me $25. They should never cost over $50. Anything more is just highway robbery. Eh?
I'm with you! I'm 35 and can remember the days of affordable parts as well... $20 to $40 is what I remember paying... What's so special about these Suzuki versions these days?!
 
#8 ·
At CAT, we found that O2 sensors get contaminated by impurities in gasoline, that alter the way the sensor works.
A new sensor is designed to run the engine a little on the lean side of perfect.
As the sensor ages it will run the engine richer and richer till it's way out of spec, wasting fuel and needs changing.
* A good test for an engine running too rich, is a buildup of soot in the tail pipe.

I changed the sensor on my Chevy X-11 at about 70k miles and I picked up about 20% increase in MPG and performance.

In 150,000 miles on my Suzuki GV, I never did change the sensors. Likewise my Suzi Forenza with 60k miles, no sensor change.
Apparently, they last longer than they did years ago.

There was/is quite a bit of O2 sensor info on the old SX4Club forum including replacement sensors at reasonable prices.

:cool:
 
#9 ·
You can try replacing the sensor, but I almost guarantee that code will come back. The converter is no longer working properly. They are covered under emissions warranty so you might as will get it fixed for free. Under warranty the front converter and the entire pipe from the rear of the motor to the muffler gets replaced (in order to replace the other converter as well). In Canada emissions warranty is 7 years 130kilometers, so you are well under that. And yes I've seen converters fail early, and some I've seen them last 250k as well. To replace both converters is well over $1000 so I suggest booking an apppointment ASAP and DONT clear the MIL.
 
#11 ·
Hmm... Well. I reset the code initially when retrieving it, and it hasn't tripped yet. So, I guess we'll see... I'm starting to lean more towards the catalytic convertor myself as well, since it's been a while now and no new code. That particular day was a really hot day, and I drove a much farther distance than usual... Perhaps the clay inside was overheating?

Good to know about the warranty! Even though it's free, however, I bet the service department will try to stick it to me somehow! Before I had my friend come over and check the code for me, the dealership quoted me $100 just to hook it up to the computer, along with their statement of "the fee would go towards any service done on the vehicle, if any service is performed" ... So, I bet I'd still get stuck with the fee (or one of another derivative), even though I already know the code and the part in question is under warranty!

I speak from experience, when I say Nickel-And-Dime-Cheeky-Bastards, since I had similar warranty/insurance (that came with my vehicle purchase) on my tire and wheels and when I went to put in a claim on one of the wheels I was told the actual cost would be close to $1000 for replacement, but the "service" or labor wasn't covered in the warranty, so my out-of-pocket was over $200... In that particular case, I ended up just buying the wheel somewhere else for around $120 (if I remember correctly) and got 4 new tires, which if added to the $120 (after dividing the tire purchase by 4), ended up being a little over the $200 for that one wheel/tire they would've fixed at the dealership for $1000... Dealership service/parts departments are ridiculous and I'm dreading dealing with them!
 
#13 · (Edited)
I sure dunno! Suzuki don't even make them.
Some big outfit like Delco, Bosch, NTK or Denso makes them, for almost all car makers.
I'll bet the auto makers don't spend more than $5 each for them.

:cool:

PS: just Google "O2Sensor" and you'll see ad's for them as low as $16.
 
#16 · (Edited)
Do those first come up as a Check Engine Light?
Solid? Flashing? Intermittent?:cool:
Hello from sunny Cyprus, Shadow.

I am not up to speed on Suzuki PCM behaviour. I usually mess with GM V8's but the DTC codes are universal (thankfully).
Though how a PCM is programmed to trip a MIL (or Engine Check Light) depends on how they are set in the car computer.

Looking at a GM tune file as an example, for each DTC they can have:-
1] 1 Trip, Emissions Related.
or
2] 2 Trips, Emissions Related.
or
3] Non-Emissions
or
4] Not Reported.

All DTC's I've seen have P0420 & 0430 (Cat Efficiency left & right bank) are set with #1 above, understandably.
So this should trigger an intermittent ECL initially (as I'd imagine a cat won't go from serviceable to completely un-serviceable instantly) then a steady ECL.
This is an educated guess!

Would imagine this would be the same in a Suzuki and most if not all other cars.
 
#19 · (Edited)
Maybe....but we do not know your model, engine type, mileage, year, where you live....so too vague to confirm or discuss.
 
#21 · (Edited)
Your base model, in Germany, may not be the base model elsewhere - if you want realistic answers then you have to provide the detail, and if you're not starting from the same P0420 code, then you'd probably be better off starting a new thread.

If you are starting from the P0420 code - why are you considering a change of O2 sensors when the code says you have a cat. converter problem?

If you're not starting from the P0420 code - why are you considering a change of O2 sensor?
 
#23 ·
G'day All,
Not to bring up old issues but I have a 09 SX4 82K in the US and have a P0420 code come up which as you know is a bad cat. I am looking at removing the cat permanently. Has anyone ever done this and how if any can you stop check engine light coming on, bypassing the code. I have successfully done this on my 99 Dodge Dakota R/T by removing the cat and strapping the O2 sensor to the underside of the body to get fresh air, no codes! I know the cat on my SX4 does not have an O2 sensor connected to it. Any help or suggestions would be appreciated.
Cheers
 
#25 · (Edited)
Thanks for that info Sid447 and others.

My '08 SX4 JLX has been giving the same code intermittently. My Autolink scanner also reads: "Catalyst System Efficiency Below Threshhold (Bank 1)".
So the issue is, is it No 1 pipe (the downpipe with cat from the manifold) or the second downstream cat. converter? The first pipe has an O2 sensor (lower port) and an Air/Fuel ratio sensor (upper port) I think. I can't imagine those sensors coming out and being reusable if the first Cat needs replacement. A local muffler shop said they could fabricate a converter and would be much cheaper than a Suzuki oem. However, those Cats can be found online for about $250 some have two ports and some have three. As far as I can see my Canadian SX4 has just two ports.

With two codes related to the Catalytic converters (P0420 and P0430) is one specific for each cat?

Thanks. :)
 
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