2005 Corolla Issues - Toyota Nation Forum : Toyota Car and Truck Forums

XoMeLLyoX · 02-13-2011, 08:33 PM

So a couple months ago my check engine light came on. I took it to Auto Zone and it gave me the P0420 code. A few days later, it turned off and hasn't come back on since. But I have noticed issues with my car's performance. I have started getting worse gas mileage. My car, when sitting idle, will shift between 600-1000 rpms. I can also hear a noise when it idles towards 600 rpms almost like I have a loose muffler. At first I thought it was possibly that my bike rack became loose but I heard the noise when I took it off. I have checked the muffler and nothing is loose. I have also noticed that sometimes when driving it has some lack in power sometimes when hitting the gas. I am going to get the ECM replaced tomorrow as part of the recall. Is it possible that it has caused all of these issues?

XoMeLLyoX · 02-13-2011, 08:56 PM

I would also like to note that when idling around 600 you can feel a vibration. And now there seems to be a clicking noise underneath the hood on the right side towards the windshield. Very odd behavior for my car.

TrdSpeed140 · 02-13-2011, 10:19 PM

the clicking is normal, that's just the vacuum switching valve working.

as for your loose muffler noise, is it like a metallic rattle? i had that problem and it turned out to be the lower half of the exhaust manifold heat shield, one of the bolts had rusted out (being the lower half i'm sure it was getting lots of spray off the road when the weather was bad).

low idle can possible be attributed to a leaking intake manifold gasket, a common problem among 1ZZ-FE engines.

W6e6s6W · 02-25-2011, 07:25 PM

P0420 is a catalytic converter code.
So after you replace the cat, it should run alot better and not throw that code.
If it was an intake manifold gasket leak it would be a P0171 (System Bank 1 Too Lean)

sgtpepper868 · 03-01-2011, 08:32 PM

Quote:

Originally Posted by W6e6s6W

P0420 is a catalytic converter code.
So after you replace the cat, it should run alot better and not throw that code.
If it was an intake manifold gasket leak it would be a P0171 (System Bank 1 Too Lean)

agreed.

catalytic converter OR possibly the downstream O2 sensor (the one attached to the cat)

P0420 is a catalytic converter efficiency code. in many cases it's not the cat, but in fact the downstream O2 sensor gone bad.

the brain compares readings from the upstream O2 sensor and downstream O2 sensor and if the downstream is showing high CO the brain will throw the code.

2005 corolla .. so it could be the cat. however, the O2 is much cheaper. so start there and then replace the cat if a new O2 didnt solve the issue.