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Another P0420 & P0430 Question

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Old 08-06-14, 03:59 PM   #1
Nosugar
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Default Another P0420 & P0430 Question

Hello everyone,

I'm new to the club. I bought my first Lexus last week, it is a 2004 GS300 and it has 183K on it. The person that had it took great care of it, but when he saw the P0420 & P0430 codes decided it was time to let it go. Unfortunately for me He didn't tell about the codes. I found out the next day when the engine light came on :-(. Anyway, I've been doing a lot of reading and learning a lot about the possible solutions, but I wanted to ask your advice regarding getting a complete exhaust from someone who is parting out with a car and use those cats to replace mine.

I also wanted to mention that the day I bought the car I took to get it smoged and it passed easy.

Thank you in advance for any guidance you may have,

Glad to be here.
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Old 08-06-14, 06:10 PM   #2
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Check for leaks first, my car had the codes when I bought it too, but a quick wave under the cats and i felt the flutter of exhaust gas and realized that the gaskets had failed after the cats, 6$ on amazon for the gaskets replaced them and the codes were gone
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Old 08-06-14, 07:08 PM   #3
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Also, if is not a leak on the muffler system, check your O2 sensor. For the miles that your car have, that is the second option to check. I just change all gasket, bolts and nut in my car 2 week a go and code go out. Good lock
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Old 08-07-14, 06:43 AM   #4
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yup just like they said, its guaranteed to be a leak or the o2 sensors but most likely a leak which is a cheap fix, be happy
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Old 08-07-14, 08:29 AM   #5
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Thanks for your responses. I took the car to a muffler shop and checked for leaks, but did not find any. Which Sensor should I replace? or do I need to do all of them?
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Old 08-07-14, 08:32 AM   #6
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those codes should be for the front ones, but at this point to save money do them all at once since eventually they will all need to be replaced anyway. It would suck to spend hundreds on the fronts just to findout you need to spend more labor on the rears
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Old 08-07-14, 08:33 AM   #7
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and MAKE SURE you call lexus and get the Denso part numbers and order them from amazon instead, its like half the price for the SAME part that they just stick in a lexus box and charge double
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Old 08-07-14, 08:51 AM   #8
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i have the same codes on my 01 gs300 but havent had time to check it please post yor results after replacing the 02 sensors
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Old 08-07-14, 08:58 AM   #9
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check for leaks, its the easiest and cheapest thing to diagnose and fix!!!! Dont even think about O2's until you rule out a leak
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Old 08-07-14, 07:52 PM   #10
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And you can also check one other thing... do you smell exhaust when you're driving? Does it smell like sulphur (rotten eggs smell) or just what would come out the tailpipe?

If it's a constant sulphur smell then you could be headed for a very expensive catalytic replacement.
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Old 08-11-14, 08:47 AM   #11
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The CEL went off out of the blue this morning. I was driving in to work and noticed that the light was off. what does this mean? I did my first fill up on Saturday and used 76 premium gas, but I don't know if that's the reason the light went off. I'll keep you posted if the light comes back.

Thanks everyone.
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Old 08-11-14, 09:36 AM   #12
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what gas where u using before?
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Old 08-11-14, 11:10 AM   #13
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The light will always go on and off. Doesn't mean the code actually went away!
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Old 08-11-14, 12:37 PM   #14
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The seller gave me the car with a full tank of gas when i bought it, so I don't know what type of gas he was using before, but he suggested I use premium so I assumed that's what he had been using.

Is there anything I can do to check if the code has gone away?
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Old 08-11-14, 01:40 PM   #15
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Yea go to autozone and get the codes red for free since I'm assuming u don't have an obd2 scanner. Also sometimes if the gas cap hasn't been fully tightened as in hearing at least 3 clicks that can throw a CEL as well
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Old 08-11-14, 01:40 PM
 
 
 
 
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