I've recently been through this learning curve.

The built-in pushbutton only reads emissions (CEL) codes, there are many codes on pins 8 and 16 that are critical and will not read from the built-in button and LED.

I built the box, using around $10-$20 of new parts from Radio shack (12v LED assembly, pushbutton, banana plugs, small plastic box) in around 30minutes and it is well worthwhile IMO. Doesn't tell you everything, but it helps.

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Gone to the dark side

- Jeff