SEAT GP-SUSPENSION 1075827 - Caterpillar

Secondary Steer Attachment
Illustration 3 g02578439
Components that are part of the secondary steer attachment (1) Ground driven secondary steering pump (2) Steering pump oil pressure sensor (6) Diverter valveWhen the Secondary Steering Attachment is installed on the machine, the components called out in illustration 3 are installed in addition to the redundant steering solenoid valves.Note: When the machine is moving, the ground driven secondary steering pump provides backup hydraulic pressure for a short time during a failure of the primary steering pump or if the engine stalls. Activation of the pump will allow continued steering operation long enough to stop the machine in a safe location. Stop the machine at the earliest opportunity and turn OFF the key start switch.Pump Pressure Sensor
When the secondary steering attachment is installed, one pressure sensor is used to monitor "resolved" pump pressure.The Steering Pump Oil Pressure Sensor provides analog voltage input signal to the Implement ECM. The Implement ECM 5 VDC power supply is used to power the sensor. This sensor provides a 0.5 VDC to 4.5 VDC voltage signal to the ECM that will correspond to the monitored pump pressure.The approximate signal voltages for the listed pump pressures are in the following table.
Table 1
Steering Pump Oil Pressure Sensor Signal Voltage versus Pressure    
Pressure     Signal Voltage     Pressure     Signal Voltage    
6895 kpa (1000 psi)     0.9 VDC     24.1 mpa (3500 psi)     2.9 VDC    
13.8 mpa (2000 psi)     1.7 VDC     25.6 mpa (4000 psi)     3.3 VDC    
17.2 mpa (2500 psi)     2.1 VDC     31.0 mpa (4500 psi)     3.7 VDC    
20.7 mpa (3000 psi)     2.5 VDC     34.5 mpa (5000 psi)     4.0 VDC    Secondary Steering System Activation and Control
When the Implement ECM detects certain failure mode conditions in the primary steering system, the ECM will notify the Machine ECM to activate the secondary steering system. The abnormal condition that is detected will determine which of the following operational modes will be activated:
The redundant steering solenoid valves can be activated only.The diagnostics that the Implement ECM uses to request that activation of the redundant steering solenoid valves is listed in prior text under the "Secondary Steering Redundant Solenoid Valve System"title.If the Implement ECM detects that the primary steering pump pressure is too low, the ECM will activate a latched level 3, E542 (Low Steering Pump Pressure) event.
Low steering pump pressure detected WITH engine rpm present and ground speed detected.
Low steering pump pressure detected WITH NO engine rpm present and ground speed detected.If the Implement ECM detects multiple abnormal conditions that require activation of the redundant solenoid valves, the ECM will request that the Machine ECM activate the secondary steer mode of operation.The Implement ECM will use Pulse Width Modulated (PWM) signals on the secondary steering request circuit (U738-PU) to notify the Machine ECM to activate and control the secondary operation. The duty cycle on this circuit will indicate the mode or operation that the Machine ECM will activate.The PWM duty