Code Details
| Display code | Navistar Aware SPN 639 FMI 2 |
|---|---|
| SPN | 639 |
| FMI | 2 |
| OEM code | Navistar / International Aware SPN 639 FMI 2 |
| Manufacturer | Navistar / International |
| System | Aware Vehicle Intelligence / Telematics |
| Component | J1939 CAN data link |
| Source address | Unknown or not applicable |
| Severity | medium |
| Review status | ai source checked |
| Source confidence | high |
| Last reviewed | 2026-03-26 |
Plain-English Meaning
The Navistar Aware module connects to the vehicle's J1939 data link to read engine data, vehicle speed, odometer, and other parameters needed for fleet reporting and telematics. When no J1939 messages arrive for 5 seconds with the ignition on, the Aware module flags this fault — it cannot read any vehicle data from the J1939 network.
Navistar S08312 maps Navistar Aware SPN 639 FMI 2 to CAN1 J1939 Network 1 — data erratic, intermittent or incorrect at Black connector Pins 9 and 10. The fault is active when no datalink messages are received for more than 5 seconds while ignition is on and J1939 communication is enabled.
Common Symptoms
- Fleet portal shows vehicle data (speed, RPM, odometer, fuel) as unavailable or not updating
- Aware module reports no engine or vehicle data in diagnostic output
- J1939-derived parameters in the Aware reporting stop updating
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- J1939 connection at Black connector Pins 9 (CAN High) and 10 (CAN Low) is disconnected, corroded, or making poor contact
- J1939 backbone fault on the vehicle — an open circuit on the J1939 bus prevents all modules from communicating, including the Aware module
- Termination resistor issue on the J1939 network — missing or incorrect termination affects all modules on the bus
- Aware module wiring to the J1939 diagnostic connector is damaged or routed incorrectly
First Checks
- Check whether other modules are logging J1939 communication faults — if the vehicle's ECM, transmission, or ABS are also showing network faults, the issue is on the vehicle's J1939 bus, not specific to the Aware module.
- Measure the J1939 termination resistance at the Aware module's connection point — the J1939 backbone should measure approximately 60 ohms across CAN H and CAN L with all modules connected.
- Inspect Black connector Pins 9 and 10 for damage, moisture, or poor contact with the mating connector.
- If only the Aware module shows the communication fault and the rest of the J1939 network is healthy, inspect the Aware module's J1939 connection at the body-builder connector.
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 Navistar Aware SPN 639 FMI 2 mean the Aware module is disconnected from the J1939 bus?
It means the Aware module is not receiving J1939 messages — which can be because its connection to the bus is broken, or because the bus itself has no traffic. Checking whether other modules on the bus are communicating normally is the key diagnostic step.
Can the Aware module still report GPS data when Navistar Aware SPN 639 FMI 2 is active?
Yes. GPS-derived data (position, heading, GPS-based speed) is independent of the J1939 connection. Fleet data that requires vehicle parameters (engine RPM, J1939 odometer, engine hours) will be unavailable, but position reporting through GPS continues if the GPS module is functioning.
Will Navistar service need to be involved to fix Navistar Aware SPN 639 FMI 2?
If the J1939 fault is isolated to the Aware module's wiring connection, the repair can typically be done by a body-builder or fleet technician by inspecting and restoring the J1939 connection at the body-builder connector. If the vehicle's J1939 bus has a broader fault, it may require Navistar service to diagnose the network issue.