Is it safe to connect or disconnect the Code Reader while the ignition is on?
No — connecting or disconnecting the Code Reader when the ignition is ON can damage both the test equipment and the vehicle's electronic components. Always turn the ignition OFF before connecting or disconnecting the Code Reader from the vehicle's Data Link Connector (DLC). (Page 6)
From the official Innova 3100 OBD2 Code Reader manual, page 6
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