CAT Engine SPN110FMI15 Fault Code: Engine Coolant Temperature : High - Least Severe (1)
Also called Engine Coolant Temperature : High - least severe, Engine Coolant Temperature : High - least severe (1), Engine Coolant Temperature: High- least severe, High Engine Coolant Temperature, High Engine Coolant Temperature - least severe, High Engine Coolant Temperature Warning, High Engine Coolant Temperaturere
Engine Coolant Temperature : High - Least Severe (1) · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 110 FMI 15 means the CAT ECM has detected engine coolant temperature above 110° C (230° F) for at least 0.5 seconds (some code bodies list 109° C / 228° F for 10 seconds). This is logged as the least severe of the high coolant temperature codes on C13, C15, and C18 engines, and the warning lamp will come on if equipped.
Medium severity. This is described as the least severe of the high coolant temperature faults, but running an engine hot for any length of time risks head gasket, water pump, and radiator damage. Treat it as a shift-stopper: diagnose before continuing heavy load work, and do not ignore repeat triggers.
What does CAT Engine error code SPN110FMI15 mean?
SPN 110 FMI 15 is Caterpillar's code for high engine coolant temperature, flagged by the ECM as the least severe stage of overheating warnings on C13, C15, and C18 engines. It means the coolant temperature sensor is reporting readings the ECM considers too hot for normal operation.
One code body states the ECM detects coolant temperature greater than 110° C (230° F) for at least 0.5 seconds, and the code resets once temperature drops back below 110° C (230° F) for at least 0.5 seconds. Another version of the same code states the temperature has been at 109° C (228° F) for 10 seconds, with the ECM powered for at least 2 seconds and the engine running for at least 185 seconds, and no electrical or battery faults present on the circuit.
In either case, the ECM logs the diagnostic code and, if the machine is equipped with one, turns on the warning lamp. This is an early-stage overheat warning, not yet the most severe stage, but it should not be ignored.
What triggers a CAT Engine SPN110FMI15 code?
The ECM sets this code when engine coolant temperature exceeds 110° C (230° F) for at least 0.5 seconds (per one code body), or when coolant temperature has been at 109° C (228° F) for 10 seconds while the ECM has been powered for at least 2 seconds, the engine has been running for at least 185 seconds, and there are no electrical or battery faults on the circuit (per other code bodies). The code clears itself once coolant temperature drops below 110° C (230° F) for at least 0.5 seconds.
Common causes of SPN110FMI15
- Other diagnostic codes present on the system that may be affecting coolant temperature readings or engine cooling performance
- Low coolant level
- Faulty or degraded coolant temperature sensor, or a faulty coolant temperature gauge
- Damaged, clogged, or restricted radiator, radiator fins, or hoses
- Bad radiator cap or pressure relief valve not holding proper system pressure
- Restriction somewhere in the coolant system
- Stuck or failing water temperature regulator (thermostat)
- Engine cooling fan not operating correctly
- Poor quality or contaminated coolant
- Failing coolant pump
- Blown or leaking cylinder head gasket
How to troubleshoot CAT Engine SPN110FMI15: first checks
- Check for other active or logged diagnostic codes before doing anything else, since related faults can point straight to the root cause
- Check coolant level when the engine is safely cool, and look for signs of external leaks at hoses, radiator, water pump, and head gasket area
- Inspect the radiator and radiator fins for debris, bent fins, or airflow restriction, and check hoses for collapse, cracking, or blockage
- Check the radiator cap and pressure relief valve for proper sealing and pressure holding
- Verify the engine cooling fan is engaging and spinning correctly at the expected times
- Inspect the water temperature regulator (thermostat) for sticking or failing to open
- Check coolant quality and condition, looking for contamination, wrong mixture, or coolant that is overdue for a change
- Have the coolant temperature sensor and, if equipped, the coolant temperature gauge tested to confirm accurate readings
How the code clears
No separate reset procedure is listed for this code. Based on the set conditions, the code clears when coolant temperature drops and stays below 110° C (230° F) for at least 0.5 seconds. Repairing the root cause, such as a low coolant level, failing thermostat, or blocked radiator, should allow the code to clear on its own once temperatures return to normal. Confirm no other coolant-related codes remain active after the repair.
Affected models and serial ranges
SPN110FMI15 appears in our records across 3 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C13 | Serial range not listed in source records |
| C15 | Serial range not listed in source records |
| C18 | Serial range not listed in source records |
Frequently asked questions
What does SPN 110 FMI 15 mean on a CAT engine?
It means the ECM has detected engine coolant temperature running high, specifically above 110° C (230° F) for at least 0.5 seconds in one version of this code, or at 109° C (228° F) for 10 seconds in another version. It is logged as the least severe stage of the high coolant temperature warnings on C13, C15, and C18 engines.
Is SPN 110 FMI 15 serious enough to stop working?
It is described as the least severe overheating code, but any confirmed high coolant temperature reading should be treated seriously. Continuing to run the engine hot risks damage to the head gasket, water pump, and cooling system components. It is safest to stop, let the engine cool, and diagnose before returning to heavy work.
What usually causes this coolant temperature code?
Common causes include low coolant level, a failing coolant temperature sensor or gauge, a clogged or damaged radiator, a bad radiator cap, a restriction in the coolant system, a stuck thermostat, a malfunctioning cooling fan, poor coolant quality, a failing coolant pump, or a blown cylinder head gasket.
Will this code clear itself once the engine cools down?
Based on the set conditions listed for this code, it should clear once coolant temperature drops below 110° C (230° F) for at least 0.5 seconds. If the underlying cooling system problem is fixed, the code should not return.
Why does the code mention no electrical or battery faults on the circuit?
That condition is part of confirming the reading is accurate. If there were electrical or battery faults on the coolant temperature sensor circuit, the ECM would likely flag those issues separately instead of, or alongside, confirming a genuine high temperature reading.
Should I check other codes before working on the cooling system?
Yes. Diagnostic codes are listed as a probable cause here, meaning other active codes on the machine could be tied to or masking the real source of the overheating. Always review all logged codes first.
Can bad coolant quality really trigger this code?
Yes. Poor quality or contaminated coolant can reduce heat transfer efficiency and contribute to higher operating temperatures, which is why coolant quality is listed among the probable causes for this fault.