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Old 08-23-2019, 12:55 AM   #73 (permalink)
Cyborg ECU
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Join Date: Mar 2011
Location: Coastal Southern California
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Black and Green - '98 Honda Civic DX Coupe
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90 day: 59.78 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
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Originally Posted by Taylor95 View Post
One of my vehicles threw a P0420 code today, and started overheating about two hours later (coming home from a trip). Is this indicative of a clogged cat? I'm wondering if this procedure would also work on a clogged cat after all of the pieces have been removed.

Another related question that may have been answered: are there proper methods for disposing of the leftover mixture after the cat is cleaned?
I disposed of my leftovers taking it with old coolant and such to our hazardous waste facility. Different states will vary.

On your core question, ... overheating is not a symptom of a P0420. However, a failing head gasket could cause an overheating situation and perhaps set off the inefficient CAT Code P0420 if the engine begins burning enough coolant and oil. It's also possible that the two events are completely unrelated. I would start by investigating the cause of the overheating.

See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.

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