Secondary Steering System

The "M" series motor graders are equipped with a secondary steering system. The Transmission/Chassis ECM and the Implement ECM work together to turn on the secondary steering system if the primary steering system fails. The Transmission/Chassis ECM and the Implement ECM monitor the left joystick, steering cylinder position sensors, pump pressure sensor, and the articulation sensors.

The Implement ECM will send a PWM signal to the Transmission/Chassis ECM if the secondary steering system needs to be activated due to a secondary steering test or a problem in the primary steering system. The duty cycle of the PWM signal will be used to determine which specific secondary steering component needs to be activated. The PWM duty cycle is as follows:

- 20 percent PWM duty cycle: Normal operation, no request to activate.

- 40 percent PWM duty cycle: Request to activate the secondary steering pump motor only.

- 60 percent PWM duty cycle: Request to activate the secondary steering pilot solenoid valves only.

- 80 percent PWM duty cycle: Request to activate the secondary steering pump motor and the secondary steering pilot solenoid valves.

The Implement ECM will send the request signal to activate the secondary steering system when any of the following machine system conditions are detected:

- An active CID 2202 FMI 12 "Steering Valve Control Module Error" diagnostic code is present.

- A failure of the main hydraulic pump.

- Steering motion is detected when no primary steering command is present.

- Steering motion is not detected when a primary steering command is present.

- Steering motion is detected in the wrong direction.

- A manual secondary steer test has been requested.

- An automatic secondary steer pump test is being performed at initial start up.

NOTE: The secondary steering system is designed to be used for a short period of time in order to move the machine to an area where a safe shutdown of machine operation can take place. Operating the secondary steer pump motor for more than a short period of time will cause the secondary steer pump motor to overheat.