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Hi,i just got a service engine light soon,i have the code p420,check emissions system.My buddy the mechanic tell's me that is maybe the catatlyic converter or a o2 sensor,he say's that it might be the sensor behind the cat?I keep hearing about what the bank is,how do i know what bank it is? I have a p420 code?,Any help,thanx
 

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eldorado billy said:
Hi,i just got a service engine light soon,i have the code p420,check emissions system.My buddy the mechanic tell's me that is maybe the catatlyic converter or a o2 sensor,he say's that it might be the sensor behind the cat?I keep hearing about what the bank is,how do i know what bank it is? I have a p420 code?,Any help,thanx
There are 4 sensors:

Bank 2, Sensor 1: In the exhaust manifold for the front cylinder bank
Bank 1, Sensor 1: In the exhaust manifold for the rear cylinder bank
Bank 1, Sensor 2: Just before (in front of) the catalytic converter
Bank 1, Sensor 3: Just after (behind) the catalytic converter

Your buddy is talking about B1S3. If you're not getting a code for B1S3, though, it's likely the converter that's toasted and in need of replacement. You can remove the B1S3 sensor and blow it out with some compressed air or use an O2-sensor-safe solvent to remove the soot and carbon and put the same sensor back in there. If the code goes away, the sensor is likely the problem. If it doesn't go away, the cat probably needs replacement. If it's the O2 sensor that's the problem, the AC-Delco replacement sensors seem to perform better than Bosch, and they're less money too.

Let us know what you find. Good luck...
 

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Discussion Starter #3
Hey michael,

I really want to say thanx for your input.I will try what you said first,i will clean the sensor like you said,then if it dosent work,i need a cat.

I am just trying to figure out how you know it's b1s3?


I will check it out this weekend,and again,thanx,


Billy
 

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P0420 is a catalyst efficiency code. If an O2 sensor is bad it will not set this code but the corresponding code for the faulty sensor.
A P0420 means the computer knows the sensors are good but the catalyst is bad. It's probably been contaminated by bad fuel or a drivability problem that went unattended in the vehicles past that degraded the catalyst.

You need to make sure the car is running in good condition and has no other faults and replace the catalyst.

If the car is less than 8 years AND 80,000 miles old the catalyst is still under emissions warranty.
 
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