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theres only one catalytic converter. but it should be refering to the oxygen sensors. if your going to change them, you should change all of them, but since i can imagine money is an issue right now in this economy, change the front one, its the main one, and the one towards the rear is the back-up one. hope this helps, goodluck.
The P0420 code is set when the oxygen sensor after the catalytic converter gives a reading the same or very close to the reading of the oxygen sensor(s) before the catalytic converter.
There are usually three possible causes... The front oxygen sensor (before the cat) is giving an incorrect reading. The rear oxygen sensor (after the cat) is giving an incorrect reading. The catalytic converter is not working properly.
Since you recently replaced the cat, the logic points to the sensors, but it could be the cat again. Aftermarket converters are usually smaller than OEM and don't last as long.
For a more thorough description of the code and troubleshooting visit http://www.obd-codes.com/p0420
Our Subaru encountered this issue several years ago under warranty. The first time the dealer replaced the front oxygen sensor. This was the cheapest repair and since it was an intermittent problem I am sure they hoped to delay the issue until the warranty was up. The second time they replaced the catalytic converter and we haven't had any more issues.
Hey I had the same code and I have a 2000 honda civic lx. My cousin
works at honda and drives a '96 honda civic and he has had that code
before on his car as well.
First thing he came up with was that the catalytic converter was
cracked. We checked mines, and lo and behold, that's what it was.
Look under your hood, and there should be a catalytic converter with a
sensor sticking out of it. It is connected to the exhaust manifold and
the sensor sticks out of the heat shield. Around the sensor, look for a
crack. If there's a crack, that's your problem.
P0041 Downstream Oxygen Sensors Swapped From Bank To Bank How does a P0041 code trigger the check engine light? This code will trigger the light to come on under the following condition:
The Heated Oxygen Sensor Monitor, a strategy built into the computer, determines if the Heated Oxygen Sensor (HO2S) signal response for a change in fuel trim corresponds to the correct engine bank. If a response from the Oxygen Sensor being tested is not indicated, a trouble code will be set and the MIL (Malfunction Indicator Lamp) will illuminate.
Possible Causes: Crossed Heated Oxygen Sensor harness connectors Wiring swapped from one Oxygen Sensor connector to the other Wiring changed at the computer connection or in the related harness
remove brackett from under intake manifold to block you will see a gray or green plug look real close and you will see a bare wire or a wire that has been pinched real bad this wire controls heater circuit for the o2 sensors also check fuse # 15.there is a tsb from honda on this problem
I had the same problem. After going through everything, it ended up being the distibutor cap. The tips were really bad. While I was in there, I replaced the rotor too. Try that. Hopefully this works for you!