Can an exhaust leak at flex pipe cause a p0420 catalyst code. Its a 2005 odyssey

 

I'm not overly familiar with how the Odyssey is set up. In my past experience, a P0420 code 99% of the time is a bad cat.

I suppose it would be possible to get a P0420 with an exhaust leak if the leak is after the first o2 sensor but before the cat but doubtful.

P0420 is a catylist efficiency code. Oxygen content is measured in the exhaust gasses both before and after the cat at the o2 sensors and based on those readings, the ECU determines if your cat is running at full efficiency. If it's even the least bit inefficient, it will throw a code. Your converter could still be working at 98% efficiency and a P0420 will still pop up.

Oxygen measured at primary 02 sensor, then the exhaust goes through the cat and oxygen is measured again at the secondary o2 sensor. The cat's job is to remove a certain percentage of the oxygen from the exhaust gas and convert it to harmless water vapour.

Obviously at different elevations, etc, there will be different o2 levels in the air so the sensors aren't looking for a fixed number, they are just looking for the difference in the o2 levels before and after the cat.

An exhaust leak before or after the cat shouldn't have any effect on the o2 readings unless the leak was in the cat itself.

I also have a P0420 on my 2002 CR-V. I may fix it eventually. Just makes me sick to my stomach thinking about replacing a $1200 part that should last for the life of the vehicle.

 

@ Goldsy: I feel ya on that. The cat for my Civic was near $1000.

@ uberEFtuner: Luckily the cat for a 2005 Odyssey is less than $200. Get under the car and LIGHTLY tap the cat. If you hear anything rattling around in there the cat is bad. You can also dis-connect the pipe and look in the cat. If it looks burnt, melted, or is crumbly the cat is bad. It's also a good idea to replace the O2 sensors at the same time as changing the cat.

 

p0420 is a cat 100% there is no 02 sensor after the flex-pipe , to replace the cat is a bitch , you will have to remove the axle, halfshaft , 4 # 12mm bolts that sometime they rust

 

Go to a dealer to see if there is a PCM update for the 420 code