Another good resource is <http://fixyourownprinter.com>. Especially for
the elusive error codes. (And Russ is right, the Apple manuals will not
give you the error code interpretation nor the 'correct' HP part
numbers. However, I've been keeping my printers alive for five or six
years now by scavanging parts from other 'deaders' so have not needed
the 'correct' part number. Just the correct part.)
Jim