Code Details
| Display code | SPN 412 FMI 0 |
|---|---|
| SPN | 412 |
| FMI | 0 |
| OEM code | None listed |
| Manufacturer | PACCAR |
| System | Engine �?EGR system |
| Component | EGR cooler / EGR 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 PACCAR MX-13 EGR cooler lowers the temperature of exhaust gases before recirculation to improve combustion and NOx control. When post-cooler EGR temperature is too high, the cooler is not removing enough heat �?either from a bypass fault routing hot gases around the cooler, or degraded cooler performance. On Kenworth T680, T880, and Peterbilt 579 trucks with the MX-13, the EGR system is managed by the ACM (Aftertreatment Control Module) and the ECM working together. DAVIE4 and PACCAR ESA provide live EGR temperature data and can command the EGR bypass valve for testing. Scale in the EGR cooler passages — from long oil change intervals or low coolant inhibitor — reduces heat transfer and is a common cause of elevated EGR outlet temperature on high-mileage MX-13 trucks in long-haul service.
SPN 412 FMI 0 is EGR Temperature above normal in J1939. On the PACCAR MX-13, DAVIE monitors EGR inlet and outlet temperatures, bypass valve position, and coolant circuit status. A stuck-open bypass valve causes uncooled EGR to enter the intake, raising both EGR outlet temperature and combustion temperatures.
Common Symptoms
- Check engine lamp active
- Higher intake temperatures from hot EGR contribution
- Possible NOx-related faults if combustion temperatures are elevated
- Elevated intake temperature visible in DAVIE4 live data alongside the fault code
- May occur together with EGR bypass valve faults
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- EGR cooler bypass valve stuck open
- Restricted coolant flow to EGR cooler
- EGR cooler core degradation
- Temperature sensor drift
- Internal EGR cooler scale from low coolant inhibitor or deferred maintenance
- EGR temperature sensor circuit fault
First Checks
- Connect PACCAR DAVIE and check EGR bypass valve position and commanded state
- Monitor EGR temperature differential across the cooler in DAVIE
- Inspect for coolant leaks from the EGR cooler circuit
- Command the EGR bypass valve through its full range in DAVIE4 and verify actual position tracks commanded position
- Check coolant condition and inhibitor concentration — depleted inhibitor accelerates EGR cooler scaling
Can I Keep Driving?
Driveable. Address promptly to prevent elevated NOx from further loading the aftertreatment system.
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
Is the EGR cooler bypass valve on the PACCAR MX-13 electrically or pneumatically actuated?
The EGR cooler bypass valve on the PACCAR MX-13 is electrically actuated �?a solenoid-driven valve controlled by the engine ECU. DAVIE can command the valve to open and close to test responsiveness. This differs from some other engines that use vacuum or engine coolant pressure to control the bypass.
How does PACCAR DAVIE diagnose EGR system faults on the MX-13?
DAVIE provides EGR cooler inlet temperature, EGR cooler outlet temperature, EGR bypass valve position and command, and EGR valve position as live data parameters. By comparing inlet and outlet temperatures with the bypass valve confirmed closed, the actual heat rejection across the cooler can be assessed. DAVIE also supports bidirectional commands to test both the bypass valve and the EGR valve.
Can the PACCAR MX-13 EGR cooler be flushed to restore heat transfer efficiency?
EGR cooler flushing to remove coolant-side scale deposits is possible and can restore some heat transfer efficiency when scaling is the cause of degraded performance. However, if the cooler core tubes are damaged or severely fouled on the exhaust side, flushing will not fully restore performance and cooler replacement is necessary. DAVIE temperature differential data before and after flushing can quantify any improvement.