you can find a users manual or troubleshooting guide for the Homelite rototiller model HTC 12, on the Homelite website. Click on the Service and Support tab and then on Operators Manuals.
There are various ways you could go about computer trouble shooting. You could consult your owners manual or ask for help on forums.
lawnandgarden.manualsonline.com/manuals/mfg/homelite
The trouble shooting codes are for people and dealerships who have a service manual for the car. Based on the code the service manual tells you what the problem is associated with and steps to diagnose and find exactly what the problem is.
Look in trouble shooting in the user's manual.
On ebay
consult the trouble shooting section of your repair manual
It could possibly be the stater, check your manual for trouble shooting
trouble shooting
sears.com has all the manuels you would need. just input your model # and it will give you a pdf to download
I did not find a manual but it seems that vendor number belongs to Husqvarna.
http://www.searspartsdirect.com/partsdirect/index.action
http://www.sears.com/shc/s/nb_10153_12605_NB_CSHome