Sarah,
This error code refers to the Lateral Acceleration Sensor (G200).
The DTC (Diagnostic Trouble Code) you have posted isn't really helpful, as it doesn't indicate what fault has been detected with the sensor (see below).
I have also attached a PDF showing the removal and installation of this sensor.
Below is taken from the Ross-Tech wikki -
http://wiki.ross-tech.com/wiki/index.php/Main_Page
01423 - Lateral Acceleration Sensor (G200): No or Incorrect Basic Setting / Adaptation
Possible Symptoms
Malfunction Indicator Light (MIL) active
Possible Causes
Lateral Acceleration Sensor (G200) Basic Setting lost/not performed
Possible Solutions
Perform Lateral Acceleration Sensor (G200) Basic Setting
See Vehicle specific Diagnostic Procedures for Details
01423 - Lateral Acceleration Sensor (G200): Electric Circuit Failure
Possible Symptoms
Malfunction Indicator Light (MIL) active
Possible Causes
Wiring/Connections from/to Lateral Acceleration Sensor (G200) faulty
Supply Voltage insufficient
Lateral Acceleration Sensor (G200) faulty
Possible Solutions
Check Wiring/Connections from/to Lateral Acceleration Sensor (G200)
Check Supply Voltage
Check Lateral Acceleration Sensor (G200) faulty
Perform Lateral Acceleration Sensor (G200) Basic Setting
Cheers
Jeff