Code Details
| Display code | SPN 102 FMI 1 |
|---|---|
| SPN | 102 |
| FMI | 1 |
| OEM code | None listed |
| Manufacturer | PACCAR |
| System | Engine — turbocharger / charge air |
| Component | Turbocharger / charge air cooler / boost pressure 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 PACCAR MX-11 is a medium-range heavy-duty engine used in Kenworth and Peterbilt trucks for regional haul and vocational applications. Like the larger MX-13, it uses a variable geometry turbocharger for boost management. Low boost pressure causes reduced power, sluggish performance, and potential increases in exhaust smoke. The most common causes are a VGT actuator that is not reaching commanded positions, a boost leak in the charge air system, or a degraded boost sensor.
SPN 102 is Engine Intake Manifold 1 Pressure in J1939. FMI 1 means the measured boost pressure is below the normal range for the current operating conditions. On PACCAR MX-11 engines, the EMS continuously compares actual boost against the commanded target. If the actual pressure falls below the target beyond the calibrated tolerance, SPN 102 FMI 1 is logged. PACCAR ESA provides live data for commanded and actual boost, VGT actuator position, and intake air temperature, which are the primary parameters for diagnosing this fault.
Common Symptoms
- Reduced power under load, particularly during hill climbing or high-demand acceleration
- Sluggish throttle response
- Black or dark exhaust smoke during acceleration
- Companion code SPN 641 FMI 7 if VGT actuator is not reaching commanded position
- Poor fuel economy
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- VGT actuator not achieving commanded position from carbon buildup or motor failure
- Boost leak from the charge air cooler, hoses, or pipe connections
- Boost pressure sensor reading below actual pressure
- Turbocharger compressor wheel or bearing degradation
- Severely restricted air filter reducing inlet flow to the turbocharger
First Checks
- Connect PACCAR ESA and compare commanded versus actual boost pressure at various load points
- Inspect all charge air cooler connections and hoses for signs of leakage — cracked elbows and loose clamps are common leak sources
- Check air filter restriction and replace if overdue
- Compare VGT actuator commanded and measured position using ESA — companion fault SPN 641 FMI 7 indicates the VGT is contributing to the boost deficit
- Verify boost sensor accuracy with a portable gauge in the intake manifold if the sensor reading seems inconsistent
Can I Keep Driving?
The MX-11 with SPN 102 FMI 1 active delivers reduced power under load. The engine remains operable but at reduced capacity. Identify and repair the boost deficit before sustained high-load operation.
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 - 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
Does the PACCAR MX-11 have the same VGT design as the MX-13?
The PACCAR MX-11 and MX-13 share the same engine architecture family and use similar VGT turbocharger designs, though the specific turbocharger units are sized differently for each engine displacement. Diagnostic procedures for VGT actuator testing using PACCAR ESA are essentially the same for both engines. Carbon fouling of the VGT vane assembly is a common root cause on both MX-11 and MX-13 engines.
Is a boost leak more common on the MX-11 or MX-13?
Boost leaks can occur on either engine, typically from age-related degradation of the charge air cooler hoses, boots, or couplers. The MX-11 and MX-13 use similar charge air system designs, so the inspection procedure is the same. A boost pressure leak test using compressed air or a smoke machine applied to the charge air circuit is the most reliable way to locate a leak regardless of engine size.
Can SPN 102 FMI 1 on the MX-11 be triggered by high altitude operation?
At high altitude, ambient air pressure is lower, which reduces turbocharger inlet density and makes it harder to achieve the same absolute boost target as at sea level. The EMS calibration accounts for ambient pressure to some degree, but at extreme altitudes, achieving sea-level boost targets may not be possible. In most cases, SPN 102 FMI 1 at altitude with no boost leak or VGT fault points to a turbocharger that is working near its capacity limit.