Error Codes - HP 8112A Operating, Programming And Servicing Manual

E21 Fail Output Amp +ve Offset test
E22 Fail Output Amp -ve Offset test
E31 to E39 Fail Overall tests
The output amplifier is faulty.
Fail Burst Counter tests
Refer to Chapter 10.1
error codes and their causes.
When the self-test is completed successfully, the instrument
automatically assumes the operating state which was active when
it was last switched off, except that the output is disabled to
protect the unit under test. If the instrument battery has failed, the
Standard Parameter Set is selected.
for more information on the
Operating 4-3