This is- once again- thanks to some German tinkerers.
For those who don't like it when their CU nods off and has to be turned off/on to recover- here's a way to turn off that behavior:
To toggle the state of the CU sleep mode:
Turn the CU off. Wait 5 seconds. Turn the CU on while holding down the 'Fuel' key.
The CU beeps- if it beeps once, sleep mode is off; if it beeps twice, sleep mode is on.
They also suggest doing a CU reset before you toggle the sleep mode. That is done by pressing the ESC key while turning on the CU.