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How does ECU/PCM affect Catalytic Converter?
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cj91745
New User
Jun 17, 2012, 9:25 PM
Post #1 of 2
(1943 views)
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How does ECU/PCM affect Catalytic Converter?
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This question is not about a specific car, but concerns 2003-4 year Toyota Matrix. In 2004, Toyota issued a TSB that said if the catalytic converter fails on a Matrix (within their usual 8yr/80k mile emissions warranty), then the mechanic should reprogram the PCM/ECU in addition to replacing the catalytic converter. I would like to understand the logic of this repair strategy. Why does the original PCM firmware need to be reprogrammed? What effect did it have on the cat?
I've heard two theories on why the PCM program needed to be updated. One was that the new program simply has more tolerant settings for emissions, so that it's less likely to report unnecessary cat failures in the future. Another theory says that the old program had an error, where it allowed some unburned gas to escape into the exhaust, thus shortening the life of the cat.
Does anyone know what the answer is? Or speculate?
Thanks. I welcome any/all ideas.
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Hammer Time
Ultimate Carjunky
/ Moderator
Jun 18, 2012, 3:30 AM
Post #2 of 2
(1897 views)
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Re: How does ECU/PCM affect Catalytic Converter?
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I would lean toward the first scenario and they just made it more tolerant. There are too many systems that would prevent a rich mixture. The 0/2 sensors are there to prevent that..
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