please help with catalytic conv - Toyota Nation Forum : Toyota Car and Truck Forums

tsx · 03-09-2011, 04:52 PM

Hello, getting a P0420 on a 4cyl 2001 Camry. From research on the web/forums determined that this most likely needs a new Catalytic converter. The point of confusion is which one, a dealer tells me there are two, one in the manifold one in the long pipe. How do tell which one has failed based on the above error code?

Thanks in advance.

csaxon · 03-09-2011, 05:06 PM

Replace Bank1 Sensor2 and that should fix it.

tsx · 03-09-2011, 05:16 PM

csaxon: thanks, but from what i have read the if it was an o2 problem i would get other faults. How confident are you in this, first hand experience?

csaxon · 03-09-2011, 05:37 PM

Cats don't usually fail. Several things such as exhaust manifold leaks etc can trigger 420. Here is an applicable corolla reference. If it is the cat then you'll probably replace this sensor anyway. Start with the sensor.

http://www.alldatadiy.com/techtips/2006/20060131c.html

tsx · 03-09-2011, 06:13 PM

csaxon, Thank you, will try this weekend, taking a seat off is easy enough. Will update.

PS. Still not clear on how many Cats there are in this model. Was told that there is one in the manifold and one in the long pipe is this correct? If so how to differentiate these based on OBD II Code P0420 - if 02 tests ok?

ghettosled · 03-10-2011, 11:29 AM

cats do go bad.

on the 4-cylinder there is a primary cat and a secondary. only the primary is monitored (its the first one connected to the exhaust manifold). i had to replace mine and bought an aftermarket one manufactured by catco and its been running good for the last 4 years and counting.

mcp · 03-12-2011, 09:36 PM

I had a P0420 code recently. The O2 sensor checked good and 2 weeks ago I changed the primary cat (exhaust manifold). So far all is good.

tsx · 03-14-2011, 06:50 PM

Thanks all, @ghettoslate I see from the above pic that the second oxygen sensor is after the bottom/second cat. Why do you think it is not monitored? I thought the cat(s) are measured by the diff between the reading of the first oxy sens and the second. If both cats are between I would think both are measured and I think this makes I hard to find which cat is bad. I could be wrong just thinking outloud

ghettosled · 03-14-2011, 07:34 PM

i think the first one determines how well the engine is running (air:fuel) and the second monitors the cat's performance. i think the secondary cat is there just to filter the exhaust a little more before being dumped.

csharp100 · 03-15-2011, 02:58 PM

Cats WILL fail but the question is WHY did the cat fail. Did you have a flashing check engine light at some point? If so, this means that fuel is dumping into the exhaust and that can be a reason the cat failed. Another reason is antifreeze in the exhaust. If none of these events occured, than chances are it could be the sensor. Need to get to the root cause instead of the surface cause.