If you have 37-40 volt at the motor and the pump is not working, check for continuity between the motor and the pump.
If there is continuity, replace the pump.
If there is no continuity, search for an open between the two.
The hydraulic pressure is provided by the pump driven by the electric motor.
April, 21, 2010 AT 1:59 PM
I replaced the pump and still no-go. Is there a control circuit or module that controls this
April, 22, 2010 AT 1:13 AM
To be more specific I have the following
Sierra 1500 4WD
Sierra 2500 4WD
Sierra 2500HD 4WD
Sierra 3500 4WD