This message is displayed when a value higher than expected has been
detected on the Generator board (A10).

Check that connector X57 is well inserted. With the connector inserted,
measure the resistance between pins 2 and 4 of connector (harness to
tubehead) that should be 13.3k ± 2% while is 14.3k ± 2% between pins 4
and 3 of the same connector; if correct values are measured, replace
before the tubehead and, eventually, the Generator board.
If incorrect values are measured, replace the tubehead and then the
Generator board.