09-28-2025, 12:29 PM
The Bobcat 736 and Its Control System Architecture
The Bobcat 736 skid steer loader was part of Bobcat’s early 2000s lineup, designed for mid-range construction, landscaping, and agricultural tasks. Bobcat, founded in 1947 in North Dakota, pioneered the compact loader market and remains a dominant force in the industry. The 736 model featured a robust hydraulic system, mechanical simplicity, and the integration of Bobcat’s BICS—Bobcat Interlock Control System.
BICS was introduced to enhance operator safety by electronically controlling loader arm and drive functions. It prevents unintended movement unless specific conditions are met, such as seat occupancy, seat bar engagement, and proper startup sequence. When the system fails or displays a “NOP” (Not Operating Properly) fault, the loader may become immobilized or partially disabled.
Understanding the BICS NOP Fault
The “NOP” message indicates that the BICS system has detected a fault preventing normal operation. This could be due to electrical, sensor, or logic errors. The system uses inputs from:
Common Causes of BICS NOP Faults
Frequent culprits include:
Diagnostic Strategy and Step-by-Step Inspection
To isolate the issue:
Solutions and Field Repairs
Depending on the root cause, solutions include:
Preventive Measures and System Longevity
To avoid future BICS faults:
Stories from the Field
In New Zealand, a Bobcat 736 refused to move during a vineyard grading job. The operator discovered a mouse nest under the seat, where wires had been chewed. After repairing the harness and installing mesh guards, the loader returned to service.
In Texas, a loader used for barn cleanup showed intermittent NOP faults. The issue was traced to a weak battery that dropped voltage during startup. Replacing the battery and cleaning terminals resolved the fault permanently.
Conclusion
The BICS NOP fault on a Bobcat 736 loader is a protective feature designed to prevent unsafe operation. While frustrating, it often stems from simple electrical or sensor issues. With a structured diagnostic approach and attention to switch integrity, operators and technicians can restore full functionality and maintain safe, reliable performance. In machines where safety and responsiveness are paramount, keeping BICS healthy is not just a technical task—it’s a commitment to operational excellence.
The Bobcat 736 skid steer loader was part of Bobcat’s early 2000s lineup, designed for mid-range construction, landscaping, and agricultural tasks. Bobcat, founded in 1947 in North Dakota, pioneered the compact loader market and remains a dominant force in the industry. The 736 model featured a robust hydraulic system, mechanical simplicity, and the integration of Bobcat’s BICS—Bobcat Interlock Control System.
BICS was introduced to enhance operator safety by electronically controlling loader arm and drive functions. It prevents unintended movement unless specific conditions are met, such as seat occupancy, seat bar engagement, and proper startup sequence. When the system fails or displays a “NOP” (Not Operating Properly) fault, the loader may become immobilized or partially disabled.
Understanding the BICS NOP Fault
The “NOP” message indicates that the BICS system has detected a fault preventing normal operation. This could be due to electrical, sensor, or logic errors. The system uses inputs from:
- Seat switch
- Seat bar switch
- Controller module
- Hydraulic lock solenoids
- Key switch and startup sequence
Common Causes of BICS NOP Faults
Frequent culprits include:
- Faulty seat switch or loose wiring under the seat
- Damaged seat bar sensor or misalignment
- Corroded connectors at the controller module
- Blown fuse or low voltage at startup
- Hydraulic lock solenoid failure or stuck valve
- Software glitch in the BICS controller
Diagnostic Strategy and Step-by-Step Inspection
To isolate the issue:
- Turn the key to ON and observe BICS indicator lights
- Check seat switch continuity with a multimeter
- Inspect seat bar switch for proper engagement and resistance
- Verify voltage at the hydraulic lock solenoids (should be 12V when active)
- Scan for fault codes using a Bobcat diagnostic tool or LED blink codes
- Wiggle harness connectors and observe light behavior
Solutions and Field Repairs
Depending on the root cause, solutions include:
- Replacing seat switch with OEM or sealed aftermarket unit
- Adjusting seat bar alignment and replacing worn bushings
- Cleaning and dielectric greasing all connectors
- Replacing hydraulic lock solenoids if resistance is out of spec
- Resetting controller by disconnecting battery for 10 minutes
- Updating software if available from dealer
Preventive Measures and System Longevity
To avoid future BICS faults:
- Inspect seat and seat bar switches monthly
- Keep connectors dry and protected from washdown
- Use dielectric grease on all exposed terminals
- Replace worn seat cushions that affect switch pressure
- Avoid jumping the system with bypass wires, which can damage the controller
Stories from the Field
In New Zealand, a Bobcat 736 refused to move during a vineyard grading job. The operator discovered a mouse nest under the seat, where wires had been chewed. After repairing the harness and installing mesh guards, the loader returned to service.
In Texas, a loader used for barn cleanup showed intermittent NOP faults. The issue was traced to a weak battery that dropped voltage during startup. Replacing the battery and cleaning terminals resolved the fault permanently.
Conclusion
The BICS NOP fault on a Bobcat 736 loader is a protective feature designed to prevent unsafe operation. While frustrating, it often stems from simple electrical or sensor issues. With a structured diagnostic approach and attention to switch integrity, operators and technicians can restore full functionality and maintain safe, reliable performance. In machines where safety and responsiveness are paramount, keeping BICS healthy is not just a technical task—it’s a commitment to operational excellence.
