Engine code 420

Asked by Jan 15, 2015 at 12:36 PM about the 2007 Pontiac G6

Question type: Maintenance & Repair

My check engine light has been on for a couple of months.  I had all o2 sensors, 2 selinoids, the catalytic converter and some type of timing manifold replaced and I am still getting the 420 code.  The mechanic has double checked everything and can't figure it out what else could it be?

4 Answers

120

Did they check for gasket leaks? I did the gaskets on my intake and was throwing those cat codes until I went back and did it right.

I'm not sure they have the car now and said they are going to check it to see if it is burning oil, is that the same thing as a gasket leak?

10

Take the positive cable off battery and leave of for about 10 15 mins put back on should solve problem

120

Yep. Aside from doing the battery thing , and to be clear I am not a mechanic, I've also read that a leaky valve cover gasket can present issues but not sure if it'll throw those codes because of it.

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