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Ron Z.
Ron Z., - Hyundai Tech -
Category: Hyundai
Satisfied Customers: 18963
Experience:  18+yrs experience. State Inspector and Hyundai Diagnostics
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Hyundai Elentra: My check engine light goes on and off my mechanic

Customer Question

My check engine light goes on and off my mechanic cannot find anything wrong?
Submitted: 2 years ago.
Category: Hyundai
Expert:  Ron Z. replied 2 years ago.
Do you happen to have any p-codes that were retrieved from the on-board computer?
Customer: replied 2 years ago.
I would have to ask my mechanic for p-codes
Expert:  Ron Z. replied 2 years ago.
It'd help us a ton, seeing as there are literally dozens and dozens of parts/sensors on this vehicle that when faulty can set the Check Engine Light. Without those p-codes, it'd be impossible to take a guess as to why the light comes and goes and be correct. If you cannot get the codes from the mechanic, you can have these p-codes read FREE (except in California) at any local "big chain" part store (ie. AutoZone, PepBoys, Advanced, etc). Once you have those codes, I'm fairly certain I can help you locate the root of the problem.
Customer: replied 2 years ago.
Great I will have to find the closest one and get it for you.
Expert:  Ron Z. replied 2 years ago.
Sounds good. Like I say, that's a huge help. Once you have the p-codes, just reply here like you have been and we can continue on from here.
Customer: replied 2 years ago.
Pep Boys wants $89.00 says it will take about an hour
Expert:  Ron Z. replied 2 years ago.
As long as you are not i CA, AutoZone will read it for Free right in their parking lot. Takes about 15 minutes. PepBoys is going to try and sell you service to fix the problem after they read it. Might want to try AutoZone or Advanced first.
Customer: replied 2 years ago.
Thanks, ***** *****
Expert:  Ron Z. replied 2 years ago.
Sounds good! I'll be here when you need me!
Customer: replied 2 years ago.
Thanks for your help
- I went to AutoZone the OEM Number to Cross: P0420
Catalytic Converter was replaced by my mechanic over a year ago. He said to ignore the check engine lights everything was fine.
-The check engine lights is out now. Should I go back to AutoZone and have troubleshooting done again? I just want to find out if a P0420 code come up while the check engine light is out.
Expert:  Ron Z. replied 2 years ago.
Unfortunately, the P0420 is a very straight forward code pointing to a failing Converter. The "catch" when installing a Converter on this vehicle is that it MUST meet Hyundai specs. If the replacement Converter was installed by cutting out the old one and welding the new one in it's place, this is a "universal" type and does not meet specs. Any sort of "discount" or a converter that doesn't meet specs will usually only last roughly a year. SO- if the code does come back as P0420, there's a very strong chance the replacement converter that was installed a year ago was of lesser quality than what Hyundai requires. Make sure there are no leaks in the exhaust system. Make sure there are no current cylinder misfires. If these check ok, unfortunately, P0420 most commonly requires a new Catalytic Converter. Please do the right thing and remember to leave a rating using the stars at the top right of this page or accept the answer so I may be credited for this Q&A. You can ask follow-up questions even after you rate or accept.