DIYbanter - Self-Diagnostic mode for GE Fridge

Does anyone know how to activate the self-diagnostic modes of a GE
GSS25JEPABB fridge? I know these side-by-side fridges have a
self-diagnostic mode to perform basic troubleshooting checks - I'm looking
for the one to cycle the fridge damper.

Also, does anyone know where I can get a current service manual for this
thing? I've found a service manual for an older version (2001 model year of
an Arctica fridge), but I have a 2003 model and a lot of the features are
different. THis manual explains some self-diagnostic modes available on the
fridge, but to enter them it assumes you have an electronic keypad. (My
fridge has knobs for temp control.)

Thanks! Steve