How to Read and Interpret Excavator Error Codes (SPN & FMI Guide)

How to Read and Interpret Excavator Error Codes

 

Modern excavators rely on electronic control units (ECUs) to monitor engine, hydraulic, and electrical systems. When a fault occurs, the ECU generates error codes—also known as Diagnostic Trouble Codes (DTCs)—to help technicians identify the issue quickly and accurately.

What Are Excavator Error Codes?

Excavator error codes are alphanumeric identifiers that point to abnormal operating conditions. These codes reduce troubleshooting time, prevent unnecessary part replacement, and improve machine reliability.

Where Do You Find Error Codes?

• Onboard Monitor: The cab display shows warning symbols and error codes.
• Diagnostic Software: Tools like Komatsu KDP, CAT ET, Hitachi Service Tool, or Doosan DMS.
• Service Manuals: Manufacturer documentation listing SPN/FMI definitions.

Understanding SPN and FMI

Most excavator codes follow the SPN–FMI format:

• SPN (Suspect Parameter Number): Identifies the component or system.
• FMI (Failure Mode Identifier): Describes how the component failed.

Example:
SPN 723 FMI 9 – Glow Plug Circuit Fault
SPN identifies the glow plug circuit, while FMI 9 indicates data outside the normal range.

How to Read an Excavator Error Code

1. Record the Code: Note the SPN and FMI from the monitor or diagnostic tool.
2. Check the Manual: Identify the related system or sensor.
3. Interpret the FMI:
   • FMI 0 – Normal
   • FMI 3 – Voltage above normal
   • FMI 4 – Voltage below normal
   • FMI 9 – Data above normal range
   • FMI 14 – Intermittent or incorrect data
4. Match Symptoms: Compare machine behavior with the code.
5. Test Components: Use multimeters, pressure gauges, or live data tools.
6. Clear the Code: Reset after repair and confirm the issue is resolved.

Common Excavator Error Codes and Fixes

Error Code	Description	Possible Cause	Suggested Fix
SPN 723 FMI 9	Glow Plug Circuit Fault	Damaged glow plug or wiring	Test glow plugs, repair wiring
SPN 14031 FMI 2	Coolant Temperature Sensor Fault	Sensor failure or harness issue	Replace sensor, inspect wiring
SPN 157 FMI 4	Fuel Pressure Low	Clogged filter or weak pump	Replace filter, test pump
SPN 910 FMI 14	ECU Communication Error	CAN wiring or ECU malfunction	Inspect CAN lines, test ECU

Scania-dc13-spn-723-fault-explained

Preventive Maintenance to Reduce Error Codes

• Inspect wiring harnesses regularly
• Replace filters on schedule
• Maintain proper battery voltage
• Keep diagnostic connectors clean
• Update ECU software when required

When to Call a Professional Technician

Repeated codes, ECU communication faults, or complex electrical issues often require certified technicians with OEM diagnostic tools.

Conclusion

Understanding excavator error codes helps technicians diagnose faults quickly and accurately. By interpreting SPN and FMI values correctly and following proper troubleshooting steps, you can significantly reduce machine downtime and improve overall reliability.