OK I came up with a GU tech sheet:
SERVICE DIAGNOSTICS CYCLE
NOTE 1. To start the Service
Diagnostics Cycle, press the
following keys, in order, in less than 6
seconds, while in standby:
Heated Dry, Normal, Heated Dry,
To Rapid advance one interval at a
time, press the Start key, noting that
unlike Standard cycles, the Diagnostics
Cycle automatically resumes
after door openings and does not
require pressing Start to resume.
NOTE 2. All LEDs are turned on in
first interval of Diagnostics as a display
test. Turn on LEDs immediately
upon receiving entry sequence (even
if door is open) but don’t start timing
until door is closed.
NOTE 3.Confusing even to me.
NOTE 4. Turns on the Clean LED
anytime an open or shorted thermistor
is detected in Interval 9. Turns on
the Sanitized LED anytime >37°C/100°F
is detected in Interval 9.
NOTE 5. On soil sensor models,
the control turns on Soaking/Sensing
LED anytime it detects the pressure
switch is closed in Intervals 7 or 4.
The Soaking/Sensing LED should not
come on in Interval 7 (unless food
soil is present), and should come on
at beginning of Interval 4. Interval 7 is
an APF enabled interval. If the control
detects pressure switch closure, then
it executes APF (5 seconds of Drain
& Fill, then 5 seconds of Fill, with
maximum of 2 APFs, no closer than
1 minute apart). APFs should only
occur if heavy food soils are present.
Interval 4 is the first drain interval.
Pressure created by initial drain pump
out should trip the pressure switch.