Code Details
| Display code | SPN 100 FMI 1 |
|---|---|
| SPN | 100 |
| FMI | 1 |
| OEM code | None listed |
| Manufacturer | PACCAR |
| System | Engine �?lubrication |
| Component | Engine oil pressure / oil pump |
| Source address | Unknown or not applicable |
| Severity | stop safely |
| Review status | source backed |
| Source confidence | medium |
| Last reviewed | 2026-06-11 |
Plain-English Meaning
Oil pressure in the MX-13 is maintained by the engine oil pump and is critical for bearing and component lubrication. When pressure drops below the minimum threshold, the ECU alerts the driver and may initiate protection derates. Continued operation with confirmed low pressure risks irreversible bearing or crankshaft damage. On Kenworth T680 and Peterbilt 579 trucks with the MX-13, SPN 100 FMI 1 is a stop-engine fault. DAVIE4 provides a fault event snapshot with oil pressure at the time of the fault and can command an oil pressure test from the diagnostic menu. The MX-13 oil pressure sensor is located at the main gallery and provides the ECM with the primary lubrication circuit reference pressure. A sensor that fails intermittently can produce a false SPN 100 FMI 1 with normal mechanical oil pressure — the mechanical gauge comparison step is essential before any disassembly.
SPN 100 FMI 1 is Engine Oil Pressure below normal. On the PACCAR MX-13, the ECU monitors oil pressure from the gallery sensor and triggers the engine protection strategy. PACCAR DAVIE provides live oil pressure data and a comparison against minimum expected values at the current engine speed and temperature.
Common Symptoms
- Oil pressure warning lamp on the Kenworth or Peterbilt instrument cluster
- Engine protection derate may be active
- Potential bearing noise in severe or prolonged cases
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Low oil level from a leak or consumption
- Oil pump failure
- Pressure relief valve stuck open
- Wrong oil viscosity
- Internal bearing wear
- Oil pressure sensor fault reading low
First Checks
- Stop the engine and check oil level on the dipstick
- Do not restart without identifying the cause
- Connect PACCAR DAVIE and verify oil pressure reading after confirming oil level is correct
- Compare DAVIE reading against a mechanical pressure gauge for sensor accuracy verification
- Install a mechanical pressure gauge at the MX-13 main gallery port and compare to DAVIE4 reading
- Check the oil level and inspect for evidence of froth or dilution in the oil
Can I Keep Driving?
Stop the engine immediately. Operating with confirmed low oil pressure risks permanent engine damage.
Related Codes
Related Lookup Pages
Sources
- PACCAR / Kenworth / Peterbilt Service Support — MX Engine Resources PACCAR Inc. · oem · accessed 2026-06-11 · confidence medium
Source: PACCAR Inc., PACCAR / Kenworth / Peterbilt Service Support — MX Engine Resources. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - PACCAR Engine Technical Services PACCAR Inc. · oem · accessed 2026-06-10 · confidence medium
Source: PACCAR Inc., PACCAR Engine Technical Services. 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 oil specification does the PACCAR MX-13 require?
The PACCAR MX-13 requires engine oil meeting API CK-4 or the previous CJ-4 specification. The recommended viscosity is typically SAE 15W-40 for normal ambient temperatures. For cold climates, SAE 5W-40 is appropriate. PACCAR recommends following the oil specification listed in the Kenworth or Peterbilt operator manual for the specific truck configuration.
How does the PACCAR MX-13 oil pump compare to similar displacement engines in terms of reliability?
The MX-13 uses a gear-driven oil pump that is generally considered reliable when the engine is maintained with regular oil and filter changes. Oil pump failures before the engine's expected service life are relatively uncommon in normal operating conditions but can occur if the oil is severely degraded, contaminated with water, or if the engine runs low on oil for extended periods.
Can an oil cooler bypass thermostat fault cause low oil pressure on the PACCAR MX-13?
An oil cooler bypass thermostat is primarily responsible for oil temperature management rather than pressure. A stuck-open bypass would cause oil to bypass the cooler �?raising oil temperature �?but would not significantly reduce main gallery pressure. Low oil pressure in the MX-13 is more typically related to oil level, pump condition, or bearing clearances.