Reading ECM disables engine?

[raygun]

'07 Pontiac Solstice 2.4, which had an aftermarket tune.

I downloaded the tune. When I started the download, a bunch of relays clicked and clacked but settled down quickly. (I've never seen that happen through scanning; not sure what was going on there.)

Once the download was complete, the car refused to start. The DIC showed the message "Engine disabled."

We rebooted the car - ie, disconnected the battery, discharged residual charge, reconnected, still disabled. I scanned it with the VCM scanner app, didn't see any codes. I went ahead and cleared the (non-existent) codes. Then, the car started.

WTF? This was slightly nerve-wracking as I was nearly left in the position of having to pay for a 1300 mile tow.

[* _ *]

That sinking feeling has came up in previous tuning sessions.

I dont have any answers or replicate the issue.

[Montecarlodrag]

The clicking noises are completely normal and expected.
The no-start should not happen but it's common on CAN vehicles.
Sometimes the network is not properly reset after a flash and one or more modules are left in a faulted status. Those modules sometimes cause a no-start problem until they are reset.
They normally reset themselves after several minutes. Disconnecting the battery for 5 min will also fix the problem. In rare occasions you need to reset the codes with a scantool.

[raygun]

Cool. At the time, I cleared the codes and the error went away.

Shrug. When in doubt, reboot.