SPN 175 FMI 0 – Oil Temperature High Warning Fault Code (Symptoms, Causes & Fix)

Mar 22, 2026

The SPN 175 FMI 0 fault code is a diesel engine fault code indicating an oil temperature high warning. This diagnostic trouble code is triggered when the Engine Control Module (ECM) detects that the engine oil temperature has exceeded the specified threshold, potentially leading to engine damage if not addressed.

What SPN 175 FMI 0 Means

The SPN 175 FMI 0 fault code signifies that the ECM has detected an abnormally high oil temperature. This condition is monitored by the oil temperature sensor, which provides a signal to the ECM. When the oil temperature exceeds the safe operating range, the ECM logs this fault to alert the operator and prevent potential engine damage.

Common Causes of This Fault Code

Low engine oil level
Faulty oil temperature sensor
Restricted oil cooler
Malfunctioning thermostat
Excessive engine load or overheating

Symptoms Drivers May Notice

When the SPN 175 FMI 0 fault code is active, drivers may notice the engine warning light illuminated on the dashboard. Additionally, there may be a noticeable increase in engine temperature readings, and in some cases, the engine may enter a derate mode to prevent damage.

How Technicians Diagnose This Fault

Diagnosing the SPN 175 FMI 0 fault code involves a systematic approach:

Begin with a visual inspection of the engine oil level and quality. Ensure the oil is at the correct level and not contaminated.
Inspect the oil temperature sensor and its wiring for any signs of damage or corrosion. Use a multimeter to verify the sensor's resistance and compare it to the manufacturer's specifications.
Check the oil cooler for any blockages or damage that could restrict oil flow and cause overheating.
Test the thermostat to ensure it opens at the correct temperature, allowing proper coolant flow.
Use an infrared thermometer to verify the actual oil temperature and compare it with the sensor readings.

Common Misdiagnosis

Technicians often misdiagnose this fault by assuming a faulty sensor without verifying the actual oil temperature. It's also common to overlook low oil levels as a potential cause or misinterpret engine load conditions as a sensor fault.

Can You Keep Driving?

While it may be possible to continue driving with the SPN 175 FMI 0 fault code active, it is not advisable. High oil temperatures can lead to engine damage, and the vehicle may enter a derate mode to protect the engine. It's best to address the issue promptly to avoid further complications.

Mechanic's Diagnostic Tip

Always verify the actual oil temperature with an infrared thermometer before replacing the oil temperature sensor. This step can prevent unnecessary sensor replacements and ensure accurate diagnosis.

Frequently Asked Questions

What should I do if I see the SPN 175 FMI 0 fault code? Check the engine oil level and quality first, then proceed with further diagnostics as outlined.
Can a faulty oil temperature sensor cause engine damage? While the sensor itself won't cause damage, it can lead to incorrect readings that prevent timely intervention, potentially resulting in engine damage.
How often should I check my engine oil level? Regularly check the oil level as part of routine maintenance, especially before long trips or heavy-duty operations.