Diagnostic testers at Autozone. Do they work?

Check engine light has been on in my Z71. Just wondering if those diagonostic testers work? Is it worth the $30 bucks they cost?
2001 reg-cag Z71

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They work after a fashion but you'll get what you pay for. Larry

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You can't buy a tester for OBDII for $30 bucks. Unless you live in Californicate, Auto Zone will read the codes for free. .

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Why won't they read the codes in the Terminator state ????

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I don't know. From what I've read in this NG, it had something to do with guys having their codes cleared and then passing the smog tests. That doesn't sound very realistic to me cause I thought they checked for more than a light in the dash. I haven't been out that way yet, but they do have their own set of rules for smog control. I wonder sometimes just how much of a difference has it made for the past 25 years or so to have "Calif Specs" versus what's good enough for the other 49. They do still have a smog problem so there are probably some who want even tougher pollution laws. .

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