In 2017 Volts, PCM fault occurs for a few seconds if ACC gas
is commanded while user presses gas pedal. PID winds up,
and when PCM fault clears, car gets a "max gas" jolt.
In 2018 Volts, PCM fault doesn't time out, which means pre-enable
doesn't work at all, and car would slowly decelerate, while openpilot
thinks it's engaged.
Vasily Tarasov
b87dc53c39