'vettes throwing a code: P0420
Thread Starter
Instructor
Joined: Aug 2007
Posts: 168
Likes: 0
From: Cherryville North Carolina
'vettes throwing a code: P0420
This code has been coming up quite a bit. I've reset it a few times but it always comes back after a day or so.
I looked up what the code meant is this is what I got:
P0420 TWC System Low Efficiency Bank 1
I then searched around and pretty sure it means my left cat is bad? I can't tell that anythings wrong with the car while driving, everything seems to be fine. Is this something I need to get checked out soon? I read that a lot of people just clear it and continue on like it's no big deal. I love cars but I'm defiantly no expert on them. In fact, I'm not even really sure what a cat does to tell you the truth. Any kind of help is appreciated. Thanks!
I looked up what the code meant is this is what I got:
P0420 TWC System Low Efficiency Bank 1
I then searched around and pretty sure it means my left cat is bad? I can't tell that anythings wrong with the car while driving, everything seems to be fine. Is this something I need to get checked out soon? I read that a lot of people just clear it and continue on like it's no big deal. I love cars but I'm defiantly no expert on them. In fact, I'm not even really sure what a cat does to tell you the truth. Any kind of help is appreciated. Thanks!
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
If the car is basically stock and high mileage, likely the stock converters are on the way out. With the number of people here who have gone to headers, you should be able to pick up a low mileage mid section for cheap with basically new converters. If you were at Carlisle, you could get them for free as the header installers usually fill the dumpsters with stock mid-sections every night.
Thread Starter
Instructor
Joined: Aug 2007
Posts: 168
Likes: 0
From: Cherryville North Carolina
If the car is basically stock and high mileage, likely the stock converters are on the way out. With the number of people here who have gone to headers, you should be able to pick up a low mileage mid section for cheap with basically new converters. If you were at Carlisle, you could get them for free as the header installers usually fill the dumpsters with stock mid-sections every night.
Le Mans Master
Joined: Sep 2003
Posts: 6,275
Likes: 226
From: Farmington CT
Cruise-In VII Veteran
If the car is basically stock and high mileage, likely the stock converters are on the way out. With the number of people here who have gone to headers, you should be able to pick up a low mileage mid section for cheap with basically new converters. If you were at Carlisle, you could get them for free as the header installers usually fill the dumpsters with stock mid-sections every night.
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Team Owner
Joined: Mar 1999
Posts: 22,025
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From: At the beach in little Rhody
1st Gear
Joined: Feb 2020
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P0420 Codes
I know this post is a bit old but I just got code P0420. Car is due for inspection but check engine light is on so I will fail.
can a novice reset this code if it’s just a “warning” for bad cat?
can a novice reset this code if it’s just a “warning” for bad cat?
Drifting
Joined: Mar 2018
Posts: 1,365
Likes: 414
From: New Jersey
You can reset it but it will most likely come back. There are a few ways you can fix this.
1. Change the catalytic converter.
2. Install a spark plug anti fouler where the rear O2 sensor goes and then install the sensor
3. You can also alter the signal to the PCM by soldering a 1 Meg resistor in seriies with the O2 sensor + signal and 1 microfarad capacitor (PCM side of resistor) into the wiring of the O2 sensor..
4. Tune out the rear O2 sensors.
1. Change the catalytic converter.
2. Install a spark plug anti fouler where the rear O2 sensor goes and then install the sensor
3. You can also alter the signal to the PCM by soldering a 1 Meg resistor in seriies with the O2 sensor + signal and 1 microfarad capacitor (PCM side of resistor) into the wiring of the O2 sensor..
4. Tune out the rear O2 sensors.
Last edited by C5MSG2004Vert; Feb 27, 2020 at 03:50 PM.
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Melting Slicks
Joined: Aug 2014
Posts: 2,468
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From: East Windsor NJ
I was thinking vacuum leak - but looks more like the cat or O2 sensor....
https://www.obd-codes.com/p0420
https://www.obd-codes.com/p0420
