2003-2009 Zt-2 Wideband has a Non Linear Wideband Output (white wire). See graph below

2006-2009 Zt-2 Wideband has two wideband outputs. The Linear Wideband Output and the Nonlinear Wideband Output, which follows a natural output curve of Bosch LSU wideband O2 sensor.
The Zt-2 Linear Wideband Output is shared with the Narrowband Output (the Zt-2 purple wire). Typically the engine management systems use only a narrowband or a wideband O2 feedback.

2010 Zt-2 Wideband has one Linear Wideband Output (white wire)

Zt-2 Linear Wideband Output transfer function is:

AFR= 2 x V + 9.6
 

2006-2009 Zt-2 Wideband
The Zt-2s purchased after September 1 2006 are equipped with the Linear Wideband Output. To set up the Linear Wideband Output please open the ZDL software V 2.0.8 or later and chose the 0-5V Linear Wideband Output from the Settings/Narrowband Output Pin menu. The Zt-2 purple wire becomes the Linear Wideband Output.

2003-2009 Zt-2 Wideband
These Zt-2 Widebands are equipped with the Nonlinear Wideband Output (the Zt-2 white wire). This output follows a natural curve of Bosch LSU wideband O2 sensor.