
On entry,  ${\mathbf{M}}<1$, 
or  ${\mathbf{NEQ}}<1$, 
or  ${\mathbf{LDYSAV}}<1$, 
or  ${\mathbf{NEQ}}>{\mathbf{LDYSAV}}$, 
or  ${\mathbf{M}}>{\mathbf{NEQ}}$, 
or  ${\mathbf{NQU}}<1$, 
or  ${\mathbf{SDYSAV}}<{\mathbf{NQU}}+1$, 
or  the BDF integrator was not previously used, 
or  the Petzold error test, if applicable, was used. 