Engine Coolant Temperature High Warning
The CAT-SKIDSTEER-110-15 (CAT Skid Steer) diesel fault code means: Engine Coolant Temperature High Warning. This is a serious severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- DIY cleaning and coolant top-off: $10-$50. Thermostat replacement DIY: $30-$80 in parts. Pro diagnosis and repair ranging from a radiator flush or thermostat swap ($150-$400) up to water pump or head gasket repair ($800-$2,500) at a CAT dealer.
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Common Symptoms
- Cab display shows E-code or SPN 110 FMI 15 warning
- Coolant temperature gauge climbing into the red or yellow zone on the dash
- Machine loses power or feels sluggish as ECM begins to derate engine output
- Warning light illuminates on the instrument panel while working
- Engine may idle up or fan speed increases as the cooling system tries to compensate
- Machine may shut down automatically if temperature continues to rise beyond warning threshold
- Steam or coolant smell near the engine compartment in more severe cases
Probable Causes (Ranked by Likelihood)
- Clogged or dirty radiator or oil cooler fins blocking airflow Very Likely
- Low coolant level due to leak or neglected maintenance Very Likely
- Debris-packed engine compartment blocking the cooling fan intake or exhaust path Likely
- Faulty or stuck-closed thermostat preventing coolant circulation Likely
- Cooling fan not operating correctly, worn belt, or failed hydraulic fan motor Possible
- Failed or out-of-range coolant temperature sensor giving a false high reading Possible
- Internal coolant leak allowing air into the system or losing coolant pressure Less Likely
Step-by-Step Diagnostic Procedure
Stop work immediately and let the engine idle for two to three minutes. Do not shut it off abruptly from full load. Watch whether the temperature gauge starts dropping at idle. If it drops back into the normal range quickly, restricted airflow or overloading is the most likely cause.
With the engine off and cooled down, open the rear door and inspect the radiator and oil cooler for packed debris, mud, grass, or dust. These machines work in conditions that clog cooling fins fast. Clean the cores by blowing compressed air from the clean side through to the dirty side, or use a low-pressure water rinse.
Check the coolant level at the overflow reservoir and at the radiator cap if accessible. The level should be between the MIN and MAX marks. If it is low, look for external leaks at hoses, clamps, the water pump weep hole, and the radiator seams before adding coolant. Use a 50/50 mix of CAT Extended Life Coolant or equivalent ethylene glycol coolant.
Inspect the radiator and oil cooler for bent fins or physical damage that blocks airflow. Also check that the fan shroud is intact and sealing properly around the fan, because a damaged shroud will recirculate hot air instead of pulling fresh air through the cores.
Start the engine cold and watch whether the cooling fan spins up and ramps with load. On machines with a hydraulic-driven fan, confirm hydraulic fan operation by listening for consistent fan speed increase as engine load increases. A belt-driven fan should spin at all times the engine runs. A fan that does not turn, slips, or runs at constant low speed is a red flag.
Check for active or logged fault codes using the cab display or CAT ET connected to the J1939 service port. Look for companion codes related to the coolant temperature sensor (SPN 110 FMI 3 or FMI 4) that would indicate a sensor circuit problem rather than a true overtemperature condition. A sensor failure can trigger 110-15 even when actual coolant temperature is normal.
If the cooling system checks out clean and coolant level is correct, suspect the thermostat. A thermostat stuck closed will cause the temperature to rise quickly at moderate loads and not respond much to idling. Replacing the thermostat is a moderate job but does not require specialty tools. Refer to the service manual for your specific model for the correct part number and opening temperature spec.
If none of the above steps resolve the code and the engine continues to overheat, connect CAT ET to read live coolant temperature data and compare it to the displayed gauge reading. Internal coolant leaks, a cracked head gasket, or a failed water pump require dealer-level diagnosis and should not be operated further without repair.
Frequently Asked Questions
What does CAT Skid Steer code 110-15 mean?
It means the ECM has detected that engine coolant temperature has risen above the normal operating range and is in the warning zone. SPN 110 is the J1939 identifier for coolant temperature and FMI 15 means the value is above normal for a warning-level condition. The machine will derate engine power progressively if the temperature keeps climbing, and it will shut down if it hits the critical threshold.
Can I keep running my skid steer with this code active?
Not without addressing the cause first. The machine will enter a power derate, which means it will feel weak and sluggish. If you keep pushing it, the ECM will eventually force a shutdown to protect the engine. Stop work, let it idle, and check the cooling system before continuing. Running a hot diesel hard causes cylinder head, gasket, and piston damage that is expensive to repair.
How much does it cost to fix code 110-15?
If the fix is just cleaning a clogged radiator or topping off coolant, you are looking at $10 to $50 in materials and your own time. A thermostat swap runs $30 to $80 in parts if you do it yourself. If you need a dealer, budget $150 to $400 for a cooling system service, or $800 to $2,500 or more if the water pump, radiator, or head gasket turns out to be the root cause.
Will the machine start and run the next time I need it after getting this code?
Yes, the machine will start again after it cools down, but the code will return as soon as the same condition occurs. If the root cause is not fixed, repeated overheating will eventually cause internal engine damage or a hard shutdown in the middle of a job. Fix the cooling system issue before putting it back to work.