Code Details
| Display code | Navistar Aware SPN 251 FMI 12 |
|---|---|
| SPN | 251 |
| FMI | 12 |
| OEM code | Navistar / International Aware SPN 251 FMI 12 |
| Manufacturer | Navistar / International |
| System | Aware Vehicle Intelligence / Telematics |
| Component | RTC module — device communication failure |
| Source address | Unknown or not applicable |
| Severity | low |
| Review status | ai source checked |
| Source confidence | high |
| Last reviewed | 2026-03-26 |
Plain-English Meaning
The RTC provides accurate timekeeping for the Aware module, which is used to timestamp telematics events and maintain accurate HOS time records. FMI 12 means the microprocessor inside the Aware module cannot reach the RTC chip — a hardware-level fault inside the module.
Navistar S08312 maps Navistar Aware SPN 251 FMI 12 to RTC Module — bad intelligent device or component. The fault sets when the Aware microprocessor cannot communicate with the RTC, or when the RTC time has exceeded the UTC accuracy limit more than 3 times in a day.
Common Symptoms
- Timestamps on Aware telematics events may be incorrect or absent
- Fleet portal event times may show as incorrect or using a default timestamp
- Events may appear out of order when compared with driver logs, GPS history, or shop repair times
- The fault may persist even when GPS position data is otherwise normal
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- RTC component inside the Aware module has failed
- RTC communication channel (typically I2C or SPI) fault inside the module
- RTC battery backup depleted — some RTC chips have a coin cell backup that maintains time when power is off
First Checks
- Confirm the fault does not clear after a power cycle — a transient communication fault may clear on restart.
- Check whether the Aware module is receiving accurate time from GPS — some Aware modules can synchronize the RTC from GPS time, which may work around a degraded RTC.
- Compare the module timestamp to a known UTC reference and note the amount of drift before clearing anything.
- Review whether the truck recently had batteries disconnected, a telematics module replaced, or firmware updated.
- Contact Navistar service if the fault persists — an internal RTC component fault typically requires module replacement.
Can I Keep Driving?
Severity depends on active status, warning lamps, affected system, and related codes. Stop safely for red stop lamps, brake warnings, oil pressure warnings, high coolant temperature warnings, severe derate, or any abnormal vehicle-control concern.
Related Lookup Pages
Sources
- Navistar Aware Vehicle Intelligence Diagnostic Trouble Codes S08312 Navistar / International Truck Body Builder · oem · accessed 2026-05-05 · confidence high
Source: Navistar / International Truck Body Builder, Navistar Aware Vehicle Intelligence Diagnostic Trouble Codes S08312. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - Navistar Engine Diagnostic Trouble Code Body Builder References Navistar / International Truck Body Builder · oem · accessed 2026-05-05 · confidence medium
Source: Navistar / International Truck Body Builder, Navistar Engine Diagnostic Trouble Code Body Builder References. This page paraphrases factual fields only and is not a substitute for the original document.
Open source
FAQ
Does an RTC fault affect engine data or HOS records?
An RTC fault affects the accuracy of event timestamps within the Aware module. Engine data, J1939 readings, and odometer values are still collected, but their timestamps may be incorrect or missing. This can affect fleet reporting accuracy and traceability of events.
Can the RTC be replaced without replacing the full Aware module?
RTC components in modules like the Aware system are typically soldered to the module's circuit board. Field-level replacement of the RTC is generally not possible — module replacement is the standard repair path.
Does Navistar Aware SPN 251 FMI 12 appear after the vehicle has been parked for a long time?
If the RTC has a coin cell battery backup and that battery is depleted, the RTC may lose its time setting during an extended power-off period. The fault may appear as the module detects the time accuracy has been lost. The backup battery is typically part of the module assembly.