Code Details
| Display code | SPN 175 FMI 0 |
|---|---|
| SPN | 175 |
| FMI | 0 |
| OEM code | None listed |
| Manufacturer | Detroit Diesel |
| System | Engine — lubrication / oil temperature |
| Component | Engine oil cooler / oil temperature sensor |
| Source address | Unknown or not applicable |
| Severity | medium |
| Review status | source backed |
| Source confidence | medium |
| Last reviewed | 2026-06-12 |
Plain-English Meaning
The DD13 engine oil temperature is measured continuously to protect the lubrication system. Oil that gets too hot loses viscosity and lubrication film strength, increasing wear on bearings, camshaft components, and cylinder walls. SPN 175 FMI 0 indicates the oil temperature sensor has reported a value above the normal range. In most cases this accompanies a cooling system problem — either the coolant is also running hot, or the oil cooler is not transferring heat effectively from the oil into the coolant circuit. Operating with high oil temperature for extended periods accelerates engine wear.
SPN 175 is Engine Oil Temperature in J1939. FMI 0 indicates a value above the normal operational range. On Detroit GHG17 DD13 engines, the oil temperature sensor is monitored by the MCM. Oil is cooled by an internal oil cooler that transfers heat to the engine coolant circuit. When oil temperature rises above the calibration threshold, SPN 175 FMI 0 is set. DiagnosticLink can display oil temperature alongside coolant temperature, making it easy to identify whether the overheat is driven by a cooling system problem or an oil cooler restriction independent of coolant temperature.
Common Symptoms
- Oil temperature warning on the instrument cluster or Virtual Technician alert
- Possible concurrent coolant temperature fault if the overall cooling system is the root cause
- Oil temperature reading above normal range in DiagnosticLink live data
- Potential for oil consumption or oil quality degradation from sustained high temperature operation
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Engine cooling system overheating — the oil cooler relies on coolant to remove heat from the oil
- Oil cooler restricted or bypassed — the cooler is not transferring heat to the coolant effectively
- Low engine oil level reducing the oil circuit's ability to regulate temperature
- Oil temperature sensor fault reading above actual temperature
- Severe engine load or operating conditions exceeding normal thermal capacity
First Checks
- Check the engine coolant temperature simultaneously — if both oil and coolant are high, the cooling system is the root cause
- Verify engine oil level on the dipstick — low oil reduces the system's ability to manage thermal load
- Connect Detroit DiagnosticLink and compare oil temperature against coolant temperature to determine whether the two are tracking together or diverging
- Inspect the radiator, coolant system, and cooling fan operation if coolant temperature is also elevated
- If coolant temperature is normal but oil temperature is high, investigate the oil cooler for internal restriction or bypass valve position
Can I Keep Driving?
Sustained high oil temperature accelerates bearing and seal wear. If both oil and coolant temperatures are elevated, reduce engine load and check coolant level immediately. If only oil temperature is high, the oil cooler system requires diagnosis before continued high-load operation.
Related Lookup Pages
Sources
- Detroit Diesel Service and Diagnostic Resources — Public Reference Detroit Diesel (Daimler Truck North America) · oem · accessed 2026-06-11 · confidence medium
Source: Detroit Diesel (Daimler Truck North America), Detroit Diesel Service and Diagnostic Resources — Public Reference. 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
Can high engine oil temperature on the DD13 cause engine damage without a coolant overheat?
Yes. If the oil cooler is restricted or bypassed, oil temperature can rise even while coolant temperature remains within normal limits. The oil cooler is the primary path for removing heat from the oil, and a failed or bypassed cooler will allow oil temperature to climb independently of the coolant circuit. Monitoring both temperatures together in DiagnosticLink is the key to distinguishing an oil cooler fault from a general cooling system overheat.
How do I test the oil cooler on the Detroit DD13?
Testing the DD13 oil cooler typically involves measuring oil temperature inlet and outlet relative to coolant temperature under load using DiagnosticLink. A properly functioning oil cooler will bring oil temperature close to coolant temperature at steady state. A large, persistent difference between oil and coolant temperature (with oil much hotter than coolant) indicates the cooler is not transferring heat effectively, pointing to an internal restriction or bypass issue.
Is it normal for the DD13 oil temperature to be slightly above coolant temperature?
Yes. Engine oil is heated by combustion and friction, and it relies on the oil cooler to transfer that heat to the coolant. Under normal steady-state conditions, oil temperature is typically 5 to 20 degrees Celsius higher than coolant temperature, depending on load. A much larger difference — especially one that increases under high load — suggests the oil cooler is not performing adequately.