What is your question?
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What is your question?
this car fail to pass emission test, but nobody know why is failing.

1 Reply
You have an OBD-II compliant vehicle. It will give some type of P series code. (Pxxxx) You need to have someone with a decent scanner retrieve this code and then you can look it up, even online in some cases. Then you can begin to determine what is wrong with your vehicle. The generic 'manufacturer control computer output ...' is too vague. There is a distinct code in your computer. I do CA Smog Diagnosis and Repair for a living. There is a code, trust me.