Some Tech2 devices may fail by randomly not connecting to the vehicle. The Tech2 would display
No communications with vehicle Check Diagnostic Link Connector. This could be a sign of a malfunctioning VCI module.
It appears that not all VCI modules are manufactured on the same quality level.
This Tech2 has a faulty VCI module.
While running a self test a similar result may appear.
It appears that two different VCI modules are manufactured and sold.
Below the two different modules, side-by-side.
Note the good VCI has the QCI number stamped on the top of the case.
Note the bad VCI has the bed jumper wires on the chip, among the lower quality solder joints
Note these components are also give-a-ways to see the better manufactured board.
Just a warning, be careful when you purchase these. In my experience, even though the seller offered a 3 year warranty, once the item was paid for, and the transaction completed, he did not respond to messages through email or even through the purchasing site. I had to purchase the new VCI if I wanted my Tech2 to work, so I went with another vendor, and looked for one that had the markings I showed above. I can't guarantee that if you order the “qc” model VCI that you will get the higher quality one, only that this worked for me.
Thank the SaabCentral.com for being the source information.
Aside from this the ODB connector may also be the root cause of communication malfunctioning.