Agilent Technologies E4406A VSA Series Programmer's Manual page 398

Error Messages
Error Message Descriptions
(-171) Invalid expression
The expression data element was invalid (see IEEE
488.2, 7.7.7.2) (for example, unmatched parentheses or
an illegal character).
This error also occurs if a command is executed that is
not valid for the current selected instrument mode. Use
INSTrument:SELect to change the mode.
(-170) Expression data error
This error is generated when parsing an expression
data element. This particular error message is used if
the device cannot detect a more specific error.
(-168) Block data not allowed
A legal block data element was encountered, but not
allowed by the device at this point in the parsing.
(-161) Invalid block data
A block data element was expected, but was invalid (see
IEEE 488.2, 7.7.6.2) (for example, an END message was
received before the end length was satisfied).
(-160) Block data error
This error is generated when parsing a block data
element. This particular error message is used if the
device cannot detect a more specific error.
(-158) String data not allowed
A string data element was encountered, but not allowed
by the device at this point in the parsing.
(-151) Invalid string data
A string data element was expected, but was invalid
(see IEEE 488.2, 7.7.5.2) (for example, an END message
was received before the terminal quote character).
(-150) String data error
This error is generated when parsing a string data
element. This particular error message is used if the
device cannot detect a more specific error.
398 Chapter 6