Clearing Diagnostic Trouble Codes on CAT 973C Track Loader

[MikePhua]

The 973C and Caterpillar’s Track Loader Evolution
The Caterpillar 973C was introduced in the early 2000s as part of CAT’s third-generation track loader lineup. Designed for heavy-duty excavation, stockpile loading, and demolition, the 973C combined the power of a dozer with the versatility of a loader. With an operating weight of approximately 60,000 lbs and a bucket capacity of up to 4.2 cubic yards, it became a preferred choice for contractors working in confined spaces where wheeled loaders lacked traction.
Caterpillar, founded in 1925, has long been a leader in earthmoving equipment. The 973C was built in East Peoria, Illinois, and featured advanced electronic monitoring systems, including the Electronic Control Module (ECM), which tracks engine performance, hydraulic behavior, and operator inputs. These systems introduced diagnostic trouble codes (DTCs) to help technicians identify faults quickly—but clearing them requires specific procedures.
Understanding Diagnostic Trouble Codes and ECM Behavior
Diagnostic trouble codes are alphanumeric fault indicators stored in the ECM when a sensor or system reports abnormal behavior. Common triggers include:

• Low hydraulic pressure
  
• Engine over-temperature
  
• Sensor voltage out of range
  
• Communication loss between modules
  
• Actuator response delay
  

Each code is associated with a specific component and severity level. Some codes are “active,” meaning the fault is ongoing, while others are “logged,” indicating a past issue that no longer persists.
The ECM stores these codes in non-volatile memory, allowing technicians to review fault history even after the machine is powered down. However, clearing codes requires more than just restarting the engine.
Steps to Clear Trouble Codes on the 973C
To clear DTCs from the ECM:

• Access the Monitoring System
  • Use the in-cab display panel or external diagnostic tool
    
  • Navigate to the “Service Mode” or “Diagnostics” menu
    
• Identify Active and Logged Codes
  • Active codes must be resolved before clearing
    
  • Logged codes can be cleared once the fault is no longer present
    
• Use the Manual Reset Procedure
  • Turn the ignition key to the ON position without starting the engine
    
  • Press and hold the “Clear” or “Reset” button on the display (if equipped)
    
  • Wait for confirmation message or flashing indicator
    
  • Turn key OFF and then ON again to verify code removal
    
• Use CAT ET Software for Advanced Reset
  

• Connect laptop with CAT Electronic Technician (ET) software
  
• Interface via 9-pin or 14-pin diagnostic port
  
• Authenticate with correct password level (typically Level 2 or 3)
  
• Select “Erase Logged Events” or “Clear Fault Codes”
  
• Save diagnostic session for recordkeeping
  

A technician in Alberta once cleared a persistent hydraulic fault code on a 973C using CAT ET after replacing a pressure sensor. The code remained logged until the ECM was manually reset through the software interface.
Precautions and Common Pitfalls
Before clearing codes:

• Always resolve the root cause of the fault
  
• Do not clear active codes without repair—this can mask serious issues
  
• Document all codes before erasing for future reference
  
• Avoid repeated resets without diagnosis, which may confuse operators or delay repairs
  
• Use only authorized software and cables to prevent ECM corruption
  

A restorer in Chile attempted to clear codes using a generic scan tool and inadvertently triggered a communication fault between the engine ECM and the transmission controller. After switching to CAT ET and reinitializing the modules, the issue was resolved.
Preventive Strategies and ECM Health
To reduce the frequency of DTCs:

• Inspect sensors and wiring harnesses quarterly
  
• Replace worn connectors with sealed OEM-grade replacements
  
• Update ECM firmware during major service intervals
  
• Monitor fluid levels and pressures with calibrated gauges
  
• Train operators to recognize early warning signs and avoid overloading systems
  

A fleet manager in Texas added ECM health checks to his semi-annual inspection protocol and reduced unexpected fault codes by 70% across his tracked loader fleet.
Conclusion and Recommendations
Clearing diagnostic trouble codes on the CAT 973C is a structured process that requires both mechanical resolution and electronic reset. Whether using the onboard display or CAT ET software, technicians must ensure that faults are properly diagnosed and documented before erasing codes.
Recommendations include:

• Use CAT ET for reliable code management and module communication
  
• Resolve active faults before attempting resets
  
• Maintain clean sensor connections and inspect harnesses regularly
  
• Document fault history for trend analysis and preventive planning
  
• Train service personnel in ECM navigation and software protocols
  

With disciplined diagnostics and proper reset procedures, the 973C continues to deliver powerful, precise performance—backed by the intelligence of its onboard systems.