George B
¯\_(ツ)_/¯
Here is a little better explanation. Two scenarios with out the candi.It is your phrase "first connecting" that I was trying to pin down.
When you power up the Tech 2, there is no "connection" by which I mean that there has been zero communications between the Tech 2 and anything in the truck. If you select say Diagnostics, the select your year, vehicle type, powertrain, engine, transmission, Transfer case, Data Display (example), Engine Data Display,,,, up to this point there has been no communications attempted by the Tech 2 and the vehicle.
Only when you select, for example "Engine Data 1",, where the next screen normally flashes "waiting for data", only then are communications attempted.
Is this where you get the error(s).
1. 2002 Envoy
Connect cable to truck and turn ignition to KOEO. Power up tech2. Gauges jump to full then zero in the cluster and DIC reads UNKNOWN DRIVER. I have to cycle the power button on the tech2 and reboot a couple times and when it doesn’t do the above shenanigans it works fine.
2. 2005 gmc canyon
Connect cable to truck and turn ignition to KOEO. Power up tech2. Don’t notice any weird shenanigans but in this case was trying to communicate with the PCM. Received a NO COMMUNICATION error. After rebooting the tech2 several times it works and I can do the operation I want to.
With the Candi on my 2013 suburban KOEO the tech2 fails to recognize the candi but after several power cycles and a wiggle of the connector at the candi it connects but it occasionally causes the truck to display weird service messages. I have reloaded the firmware and tried a new main cable.
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