p0420 code ? parameters of readings
09-04-2009, 02:04 PM
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p0420 code ? parameters of readings does anybody know the stock parameters readings from the computer. i am throwing code p0420, i have a scanner that reads live info. i dont see anything wild as far as numbers, but would like to know if there is a number it should be at or close to what it should read. there are no exhaust leaks and the cat was replaced at 30,000 miles along with a sensor. i now have 69,000 miles, it seems to bog a little and when i held the rpm at 1300 it seems to shudder and run rough.i do have numbers from the scanner cold and warmed up. i am trying to save money on diagnostics from the dealer, unemployed due to accident not my fault so im not trying to be cheap. thank you for any help jim i have been using the search to no avail
09-04-2009, 04:21 PM
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forgot to mention, car is a 2002 ss 6 speed, stock except k&n filter and cai. i dont see how that would affect anything, i do clean and oil the filter sparingly. fresh oil change, i have had this code for awhile roughly 10,000 miles ago.
09-04-2009, 05:47 PM
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P0420 means the PCM has failed your LHS catalytic converted based on the response time of the rear O2 sensors...
If you scantool allows, read the Mode $6 data and look at test Test ID 0C:60, it will show you that the subtest has failed...
When the drive cycle conditions are met (freeway cruising followed by coastdown followed by idle), the PCM will briefly manipulate the AFR and time the response from front O2 sensor to rear O2 sensor... if the response time is too short it will fail the cat (TID 0C:60 fails which causes P0420).
A bad O2 sensor may actually make the cat test pass.
An airleak may help it fail easier, maybe.
The shudder/roughness is not related unless the cat is falling apart and clogging the exit pipe restricting exhaust flow.
If you scantool allows, read the Mode $6 data and look at test Test ID 0C:60, it will show you that the subtest has failed...
When the drive cycle conditions are met (freeway cruising followed by coastdown followed by idle), the PCM will briefly manipulate the AFR and time the response from front O2 sensor to rear O2 sensor... if the response time is too short it will fail the cat (TID 0C:60 fails which causes P0420).
A bad O2 sensor may actually make the cat test pass.
An airleak may help it fail easier, maybe.
The shudder/roughness is not related unless the cat is falling apart and clogging the exit pipe restricting exhaust flow.
09-04-2009, 07:40 PM
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thank you for the reply, i wasnt sure if the scanner would show a difference in readings. so as to pinpoint what is actually not working correctly. i will take a drive and figure it out. thank's again jim
09-08-2009, 02:26 PM
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.....http://gearchatter.com/ here is the site i found that tells you what tests to do. i have a ob2 scanner, i guess you would need to have or find someone that has one to perform the tests. so far ive cleared the code, and followed the instuctions given. it states you may need to perform it several times for the code to return.
