Combine Harvester Machine: Fault Codes, Warning Lights & Performance Issues Explained
Modern combine harvesters are highly advanced agricultural machines that rely on electronic control systems, sensors, and ECUs to manage harvesting, threshing, separation, and grain handling. When something goes wrong, the machine alerts the operator using fault codes and warning lights.
Understanding these fault codes and warning symbols is essential to:
Prevent breakdowns during harvest season
Avoid crop losses
Reduce repair costs
Improve machine performance and lifespan
This complete guide explains combine harvester fault codes, warning lights, common performance issues, causes, and how service manuals help fix them correctly, supported by clear technical diagrams.
How Combine Harvester Diagnostic Systems Work
Modern combine harvesters use Electronic Control Units (ECUs) connected to multiple sensors across the machine.
System Overview
✅ Sensors monitor speed, temperature, pressure, and load
✅ ECU analyzes data continuously
✅ Abnormal readings trigger fault codes
✅ Warning lights appear on the display panel
This system allows early fault detection before major damage occurs.
Understanding Combine Harvester Fault Code Format
Most modern combines use SPN–FMI or DTC-based diagnostic codes.
Fault Code Components
SPN (Suspect Parameter Number) – Identifies the faulty system or sensor
FMI (Failure Mode Identifier) – Describes the type of failure
Occurrence Count – Shows how often the fault occurred
This format helps technicians pinpoint the root cause quickly.
Common Combine Harvester Warning Lights Explained
Engine Warning Light
🔴 Engine performance or protection issue
Causes: overheating, low oil pressure, sensor faults
Hydraulic System Warning Light
🔴 Hydraulic pressure or temperature problem
Causes: low oil, clogged filters, pump failure
Grain Loss Warning Light
🟡 Excessive grain loss detected
Causes: incorrect settings, worn components
Separator / Threshing Warning Light
🟡 Threshing or rotor malfunction
Causes: belt slip, overload, sensor error
Electrical / Battery Warning Light
🔴 Charging or voltage issue
Causes: alternator failure, wiring damage
Common Combine Harvester Fault Codes & Meanings
Engine Fault Codes
✅ SPN 110 FMI 3 – Engine coolant temperature voltage high
✅ SPN 100 FMI 1 – Engine oil pressure below normal
✅ SPN 94 FMI 4 – Fuel pressure too low
✅ SPN 91 FMI 0 – Throttle or speed sensor fault
Hydraulic System Fault Codes
✅ SPN 524 FMI 9 – Hydraulic oil temperature too high
✅ SPN 523 FMI 7 – Hydraulic pressure sensor not responding
✅ SPN 520 FMI 5 – Control valve circuit error
Threshing & Separation System Fault Codes
✅ SPN 700 FMI 2 – Rotor speed above normal
✅ SPN 702 FMI 4 – Threshing drum speed too low
✅ SPN 705 FMI 7 – Separator sensor not responding
Grain Handling & Cleaning System Fault Codes
✅ SPN 750 FMI 3 – Cleaning fan speed too high
✅ SPN 752 FMI 1 – Grain elevator blockage detected
✅ SPN 754 FMI 5 – Loss sensor circuit fault
Electrical & CAN Communication Fault Codes
✅ SPN 639 FMI 9 – Lost communication with control module
✅ SPN 168 FMI 4 – Battery voltage below normal
✅ SPN 628 FMI 2 – ECU internal fault
Common Combine Harvester Performance Issues Explained
1. Poor Grain Separation
Causes:
Incorrect rotor or concave settings
Worn threshing components
Sensor calibration issues
2. High Grain Loss
Causes:
Incorrect sieve or fan settings
Overloading
Faulty loss sensors
3. Engine Power Loss
Causes:
Fuel system restriction
Turbo or air intake issues
Engine fault codes active
4. Hydraulic Overheating
Causes:
Low hydraulic oil level
Clogged oil cooler
Pump inefficiency
5. Frequent Fault Code Warnings
Causes:
Wiring damage
Sensor contamination
ECU software issues
Can You Keep Working with Warning Lights On?
⚠ Minor warnings: Proceed carefully and monitor
⛔ Engine, hydraulic, or separator warnings: Stop immediately
Ignoring warnings during harvest can lead to catastrophic failures.
Why a Combine Harvester Service Manual Is Essential
A fault code alone does not explain how to fix the problem.
Service Manual Benefits
✅ Step-by-step troubleshooting
✅ Detailed wiring diagrams
✅ Sensor testing values
✅ Hydraulic & engine schematics
✅ Calibration procedures
✅ Maintenance schedules
Service manuals prevent guesswork repairs and save time during peak harvest season.
Operator Manual vs Service Manual
| Operator Manual | Service Manual |
|---|---|
| Basic operation | Advanced diagnostics |
| Safety info | Fault code explanations |
| Daily checks | Repair procedures |
| No wiring diagrams | Full schematics |
👉 For fault codes & performance issues, service manuals are essential.
Preventing Fault Codes & Performance Problems
✅ Perform scheduled maintenance
✅ Use correct oils & filters
✅ Clean sensors regularly
✅ Inspect wiring and connectors
✅ Follow service manual settings
Preventive maintenance significantly reduces downtime.
Final Conclusion
Understanding combine harvester fault codes, warning lights, and performance issues is critical for efficient harvesting and machine longevity. However, accurate troubleshooting requires proper service manuals with technical diagrams and procedures.
Using correct diagnostic information ensures:
Reduced downtime
Lower repair costs
Maximum harvesting efficiency
FAQ Schema Questions?
What do fault codes on a combine harvester mean?
They indicate electronic or mechanical problems detected by the machine’s ECU.
Are fault codes the same on all combine harvesters?
No, codes vary by brand and model, but formats are similar.
Can fault codes clear automatically?
Some temporary faults may clear, but underlying issues must be fixed.
Should I stop harvesting if a warning light appears?
Yes, for engine, hydraulic, or threshing warnings, stop immediately.
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Repeated fault codes
Warning lights during harvesting
Hydraulic overheating
Grain loss problems
A proper service manual from ManualsBay gives you:
✔ Exact fault code meanings
✔ Step-by-step repair procedures
✔ Sensor testing values
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👉 This ensures faster repairs, less downtime, and maximum harvesting efficiency.
