Code Details
| Display code | SPN 412 FMI 0 |
|---|---|
| SPN | 412 |
| FMI | 0 |
| OEM code | None listed |
| Manufacturer | Mack |
| System | Engine �?EGR system |
| Component | EGR cooler / EGR bypass valve / temperature 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 EGR cooler reduces hot exhaust gas temperatures before recirculation into the intake. When post-cooler EGR temperature is too high, the cooler is underperforming �?from a bypass valve fault, restricted coolant, or degraded core. The Mack MP8 and Volvo D13 share the same EGR cooler architecture, so the same diagnosis approach applies to both. On Mack Anthem, Pinnacle, and Granite trucks with the MP8, the EGR bypass valve is an electronically controlled actuator. VCADS Pro (PTT) commands the bypass valve to various positions during testing and reports actual position. A valve that does not track commanded position indicates a mechanical or actuator failure. Scale buildup inside the EGR cooler passages — from deferred coolant maintenance — is a known cause of reduced heat transfer on the MP8, leading to elevated outlet temperature without a bypass valve failure.
SPN 412 FMI 0 is EGR Temperature above normal. On Mack MP8 EMS3, VCADS Pro provides EGR cooler inlet and outlet temperatures, bypass valve position and commands, and coolant temperature data for EGR thermal performance diagnosis.
Common Symptoms
- Check engine lamp active
- Higher intake temperatures
- Potential NOx increase loading aftertreatment
- Higher than expected intake temperatures visible in VCADS Pro live data
- May accompany coolant loss if the EGR cooler has developed an internal leak
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- EGR bypass valve stuck open
- Restricted coolant supply to EGR cooler
- EGR cooler core degradation
- Temperature sensor fault
- Scale buildup in EGR cooler passages from deferred coolant maintenance
- Actuator failure preventing bypass valve from closing to the cooler path
First Checks
- Connect VCADS Pro and command EGR bypass valve open and closed to test responsiveness
- Monitor EGR inlet vs. outlet temperature differential with bypass confirmed closed
- Check coolant condition and flow circuit to the EGR cooler
- Command the EGR bypass valve through its full travel in VCADS Pro and observe actual position feedback
- Monitor EGR inlet and outlet temperature differential in VCADS Pro under load to quantify cooler performance loss
Can I Keep Driving?
Driveable; elevated EGR temperatures can accelerate NOx production and aftertreatment loading.
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
Is the Mack MP8 EGR cooler bypass valve the same part as the Volvo D13?
The Mack MP8 and Volvo D13 share the same EGR system hardware in most configurations. The EGR bypass valve is typically the same part between the two platforms. Confirm part numbers via VCADS Pro or the Mack/Volvo parts portal for the specific model year and configuration.
How does the EGR temperature fault on the MP8 affect the aftertreatment system?
High EGR outlet temperature means hotter air entering the intake, which can raise combustion temperatures and engine-out NOx. Elevated NOx requires greater SCR conversion and DEF consumption. If the condition persists, it may contribute to accelerated DPF loading and SCR efficiency decline.
Can VCADS Pro quantify how much heat the Mack MP8 EGR cooler is rejecting?
Yes. With the EGR inlet temperature and outlet temperature both displayed in VCADS Pro live data, the temperature differential (inlet minus outlet) directly indicates how much heat the cooler is removing from the EGR gases. A healthy cooler typically drops EGR temperature by 150 to 300°C depending on load and EGR flow. A reduced differential confirms degraded cooler performance.