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post #1 of 5 (permalink) Old 07-22-2019, 10:32 PM Thread Starter
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P0420 code

If this code pops up does the car normally over heat has anyone had this code with 2009 Saturn sky.
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post #2 of 5 (permalink) Old 07-23-2019, 12:01 AM
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Originally Posted by Farmgirl51070 View Post
If this code pops up does the car normally over heat has anyone had this code with 2009 Saturn sky.
P0420 indicates a problem with the catalytic converter, or the post-cat oxygen sensor. There is no direct connection to overheating, although if you are losing coolant into the engine you can trigger this code, and low coolant could result in overheating.

Can you share any more details?

Lexington, KY
Sky NA 2007 Midnight Blue
Sky RL 2008 Carbon Flash - Naked

Last edited by JohnWR; 07-23-2019 at 09:15 AM. Reason: extra "be" removed
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post #3 of 5 (permalink) Old 07-23-2019, 09:02 AM
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Yeah, I'm a bit confused by the overheating comment.

One thing that could possibly cause overheating AND 0420 code is if your cat is blocked (the interior mesh has broken up and clogging the exhaust path). Only solution in that case is to replace the cat.

Owner of "Campbelle", a Brazen 2008 GXP ... with mods piling up...
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post #4 of 5 (permalink) Old 07-23-2019, 09:25 AM
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I was.. "corn-fused" by this also. You guys know the electronics of our cars better then I do here.
A 420 code... your car is high.

Two separate issues here. The code will need to be addressed by the dealer at some point.
IS it the post-cat O2 sensor? Starting point. Could the cat be blocked up? IDK. Maybe..

Over heating issue. Just started with this code, or has it been a problem before and you just noticed it now?
Miles on the odo? No work done previously? No loss of fluid in the expansion tank? No puddle under the car?
At what heat range are you seeing the over heating issue example: Above 220 degrees? Less or more than?

More info is needed here to a find a clue as what you are experiencing with your code and over heating issues.

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post #5 of 5 (permalink) Old 07-25-2019, 10:23 PM
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If you have the NA motor, the cat plugging up is a common problem with the 2.4L around the 40k-65k mark. Sometimes later depending on how the car was drivne
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