Code Details
| Display code | SPN 102 FMI 1 |
|---|---|
| SPN | 102 |
| FMI | 1 |
| OEM code | None listed |
| Manufacturer | Mack |
| 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 | 2026-06-11 |
Plain-English Meaning
The Mack MP8 uses a VGT turbocharger to maintain precise boost at all operating conditions. Low boost relative to the commanded target results in reduced power, slower DPF regen performance, and potentially higher exhaust smoke. The source of the deficit �?VGT fault, boost leak, or sensor �?needs to be identified before the issue worsens. On Mack Anthem, Pinnacle, and Granite trucks with the MP8, SPN 102 FMI 1 is commonly associated with charge air system integrity issues. VCADS Pro (PTT) provides live boost pressure data and allows the technician to assess boost pressure performance across the RPM range. A charge air pressure leak test (pressurizing the charge air system with the engine off) identifies cracks in intercooler cores, loose hose clamps, or split hoses. The Mack MP8 and Volvo D13 share the same turbocharger and charge air architecture, so the diagnostic process is identical.
SPN 102 FMI 1 is Intake Manifold Pressure below normal. On Mack MP8 EMS3, VCADS Pro provides commanded boost target and actual manifold pressure side by side. A VGT actuator test in VCADS Pro confirms whether the vane mechanism responds to commanded positions.
Common Symptoms
- Reduced power under load
- Slower or failed DPF regen cycles
- Possible smoke under load
- Reduced power particularly during grades or heavy load acceleration
- May appear with EGR-related companion codes
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- VGT actuator fault
- Charge air system boost leak
- Restricted air filter
- Turbocharger compressor wheel damage
- Boost pressure sensor fault
- Charge air cooler (intercooler) core crack or hose connection leak
- Boost pressure sensor wiring fault or failed sensor
First Checks
- Connect VCADS Pro and compare commanded vs. actual boost at various load points
- Inspect charge air hoses and clamps for leaks or loose connections
- Check air filter restriction indicator
- Run VGT actuator test in VCADS Pro
- Perform a charge air system pressure leak test to detect hose and intercooler leaks
- Connect VCADS Pro and compare live boost pressure to expected values across the load range
Can I Keep Driving?
Driveable with reduced performance. Low boost can also impair DPF regen, which may lead to DPF-related codes.
Related Codes
Related Lookup Pages
Sources
- Mack Trucks Service Support Public Resources Mack Trucks Inc. · oem · accessed 2026-06-11 · confidence medium
Source: Mack Trucks Inc., Mack Trucks Service Support Public Resources. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - Volvo Trucks / Mack Trucks Technical Support Volvo Trucks North America / Mack Trucks Inc. · oem · accessed 2026-06-10 · confidence medium
Source: Volvo Trucks North America / Mack Trucks Inc., Volvo Trucks / Mack Trucks Technical Support. 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 Mack MP8 use the same VGT turbocharger as the Volvo D13?
The Mack MP8 and Volvo D13 are closely related platforms and use similar turbocharger designs. Specific turbocharger assemblies and actuator part numbers may differ between applications depending on the engine rating and emissions calibration. VCADS Pro part look-up can confirm the correct turbocharger part number for a specific unit.
How does low boost affect DPF regen on the Mack MP8?
Active DPF regen requires high exhaust temperatures in the aftertreatment system, which depends on both adequate fuel delivery and sufficient airflow for complete combustion. Low boost reduces the density of the air charge, which can limit the maximum exhaust temperature achievable during regen and extend regen duration or cause regen to fail to complete.
Can a boost leak be heard from outside the truck on the Mack MP8?
Large boost leaks can sometimes produce an audible hiss under load. Smaller leaks may be silent at idle but produce a noticeable power deficit. The most reliable detection method is a charge air system pressure test, using shop air or a smoke machine, to identify the precise location of the leak.