Car Questions
RepairPal is your advocate for car care advice and guidance

Could a Exhaust leak cause P0420?

(1999 Toyota 4Runner)
in Portland, OR on April 27, 2010
I recently have been getting the P0420 code in my 4runner with CA emissions. Which means I have two catalytic converters. I took it into a shop where they took the voltage readings for the o2 sensors and they said it looked good. I was under the hood playing with the throttle while passing "Seafoam" through to clean the engine and noticed that some of that seafoam smoke was coming from in between exhaust pipes. The leak is at the connection right after the headers so I'm assuming it is just bad gaskets. I get the CEL P0420 code usually under hard accelerations, rainy weather, or stop and go driving. Unusual thing is that when I took it for a road trip from Portland to San Diego, and also from Portland to Seattle, the code never came on! Please help!!
Displaying 1 answers & 0 comments
Popular Answer
on April 27, 2010
Here is a ton of great info about the P0420 code, what causes it to come on and how to diagnose it:
RepairPal estimates are guaranteed at over 2,000 quality certified locations nationwide. Learn more

Similar Questions

View answers to similar questions from RepairPal's community of auto experts and enthusiasts.
There are 2 vacuum line ports at the back of the motor one is replaceable and the other is steel stationery. Another ...
I have a vibration coming through the steering wheel at around 40 to 50 mph and at other times it is fine especially ...
Didn't find what you were looking for?