Code Details
| Display code | SPN 110 FMI 0 |
|---|---|
| SPN | 110 |
| FMI | 0 |
| OEM code | None listed |
| Manufacturer | Cummins |
| System | Engine �?cooling system |
| Component | Engine coolant temperature sensor / cooling system |
| Source address | Unknown or not applicable |
| Severity | stop safely |
| Review status | source backed |
| Source confidence | medium |
| Last reviewed | 2026-06-11 |
Plain-English Meaning
The ISX15 cooling system keeps combustion temperatures in a safe operating range using a coolant-to-air heat exchanger (radiator), a coolant pump, and thermostat controls. When coolant temperature exceeds the high-temperature threshold, the engine is transferring more heat than the cooling system can handle. This requires immediate investigation to prevent permanent engine damage.
SPN 110 is Engine Coolant Temperature in J1939. FMI 0 indicates the measured temperature is above the high-temperature warning range. On Cummins CM2350, the coolant temperature sensor is in the coolant circuit at the engine outlet. The ECM uses this reading for fan drive control, fuel injection timing adjustment, and engine protection. A persistent FMI 0 reading at normal highway load conditions indicates a cooling system fault rather than the occasional high reading seen in stop-and-go traffic or heavy load at idle.
Common Symptoms
- High coolant temperature gauge reading
- Coolant temperature warning lamp or protection lamp active
- Engine protection derate may be active concurrently
- Steam or coolant smell in severe cases
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Low coolant level from a leak or coolant loss
- Thermostat stuck in the closed position preventing coolant flow
- Radiator plugged with debris or insects reducing cooling capacity
- Cooling fan clutch not engaging or engaging late
- Water pump failure reducing coolant flow
- Coolant temperature sensor fault providing an incorrect high reading
First Checks
- Check coolant level in the expansion tank immediately
- Verify the cooling fan is engaging when coolant temperature is elevated
- Inspect the radiator face for debris or insect blockage that restricts airflow
- Connect Cummins Insite and monitor coolant temperature alongside the fan engagement status to confirm correct fan behavior
- Check for coolant leaks externally and internally (milky oil, white exhaust smoke may indicate head gasket issues)
Can I Keep Driving?
Reduce load and pull over if possible when this fault is active. Operating at elevated coolant temperature risks head gasket, cylinder head, or engine block damage. A moderate temperature rise may self-correct at highway speed with adequate airflow, but a persistent rise requires stopping.
Related Codes
Related Lookup Pages
Sources
- Cummins INSITE Service Tool — Public Reference Documentation Cummins Inc. · oem · accessed 2026-06-11 · confidence medium
Source: Cummins Inc., Cummins INSITE Service Tool — Public Reference Documentation. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - QuickServe Online Cummins Inc. · oem · accessed 2026-05-05 · confidence medium
Source: Cummins Inc., QuickServe Online. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - SAE J1939 Standards Collection SAE International · official · accessed 2026-05-05 · confidence medium
Source: SAE International, SAE J1939 Standards Collection. This page paraphrases factual fields only and is not a substitute for the original document.
Open source
FAQ
What is the normal operating temperature range for a Cummins ISX15 or X15?
Normal operating coolant temperature for the ISX15 and X15 is typically 180 to 200°F (82 to 93°C) under normal highway load. The high-temperature warning threshold is calibrated in the ECM above this range. Readings approaching 220°F (104°C) at highway load indicate a cooling system problem that requires investigation.
Can a clogged EGR cooler cause high coolant temperatures on the Cummins ISX15?
The EGR cooler on the ISX15 uses engine coolant to cool recirculated exhaust gases. A severely restricted EGR cooler can add significant heat load to the cooling circuit, contributing to higher coolant temperatures, especially under high EGR flow conditions. If other EGR-related codes are also present and the cooling system hardware appears normal, the EGR cooler should be evaluated.
Should I add cold water directly to a hot Cummins ISX15 engine that has overheated?
No. Adding cold liquid to an overheated engine can cause thermal shock, cracking cylinder liners, cylinder heads, or the engine block. Allow the engine to cool down naturally before opening the cooling system. Once cool, inspect the coolant level and look for the cause of overheating before adding coolant and restarting.