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Discussion Starter · #1 ·
2007 Suzuki Sx4 crossover auto 137k..About every 300-500 the CEL comes on P0420. At 125k the Cat was replaced (direct fit). 02 sensor down stream was replaced at 135k used a Bosch Smartlink. Had to cut my harness for it.
New NGK Iridium plugs air filter at 135k.

So I am not sure what else to try. The CEL just keeps coming back with the same code P0420..

I have searched for weeks with not luck on what do try next. Could it be that the Bosch o2 sensor is not good for the Sx4?

Thank you
 

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Which cat was replaced? Upstream or down?


This is the one you need.
 

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Discussion Starter · #3 · (Edited)
Sorry upstream. Also the Upstream o2 looks old not sure if it was replaced. I am going to buy that today. Just in case. BTW the car great power, idles good, runs great even with the CEL on?
 

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The worse thing about an OLD O2 sensor is that they will cause the engine to run RICH, thus wasting gas. You may or may not notice the loss of engine efficiency.
That can happen anywhere after about 60k miles.

:cool:
 

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Discussion Starter · #5 ·
TheShadowFL can the Upstream o2 cause the code P0420?
 

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Sorry, I don't know.
In many years of driving Suzukis, I never had such a code and never replaced an O2 Sensor. I always traded off the car, before it needed one.

My experience with 02 sensors, predated my Suzukis.


:cool:
 

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The down steam o2 sensor is the one that monitors the efficiency of the cat by comparing the signal to the upstream o2.

In my experience, that code has always been caused by a faulty cat.

The reason the cat usually goes bad is a relult of low quality gas or fouled plugs causing intermittent misfires..
 

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Discussion Starter · #8 ·
ok so if the code keeps coming back after being reset in about 300-500. with P0420 and its the cat. How do I know which cat to replace? it has 2
 

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Only the front cat is monitored.
It's the only one that would set that code.
 

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Discussion Starter · #10 ·
ok Ill order a new one. Also I think the rear cat is broke cause I can hear it rattle a little. But it cant set the code right?
 

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No the rear one won't set that code.
 

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so how hard of a job is it replacing the O2 sensor? i'm getting the same 0420 code and was recommended that I start there to resolve
 

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Discussion Starter · #13 ·
Replacing the O2 sensor is very easy. Also incase you have to replace the CAT it is easy as well... Good Luck
 

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Discussion Starter · #14 ·
OK so far the P0420 code is gone and FIXED....
I tried a product called CATACLEAN. I followed the instructions and after 223 miles the CEL went out for the first time in over 8k. So I reset the computer and after 600+ more miles still no CEL :)
Thanks for the help
 

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Po 420

HI I have suzuki for 1 year when but I have problem po420 mechanic said is the cap when put gas , after 4 month ligth come back on again I bring too mechanic he change o2 sensor now ligth come back on what is te problem now I pay 500 dollar for change the sensor please what you thing is the problem in my suzuki
 

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I think the problem is the upstream catalytic converter.

You can help us out by giving us year and model of your car.
Plus a location helps too.
 
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