With Electro-Hydraulic Steering

Diagnostic Starting Point - Power Steering System (w/ Electro-Hydraulic Steering)
Begin the system diagnosis with the Diagnostic System Check - Power Steering System. You may want to review the Power Steering System Description and Operation (w/o Electro-Hydraulic Steering) Power Steering System Description and Operation (w/ Electro-Hydraulic Steering) before beginning the diagnosis. The Diagnostic System Check will provide the following information:
^ The identification of the control modules which command the system
^ The ability of the control modules to communicate through the GMLAN circuits
^ The ability of the control module to communicate through the serial data circuit
^ The identification of any stored diagnostic trouble codes (DTCs) and their status

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.