Code Details
| Display code | Navistar Aware SPN 1079 FMI 0 |
|---|---|
| SPN | 1079 |
| FMI | 0 |
| OEM code | Navistar / International Aware SPN 1079 FMI 0 |
| Manufacturer | Navistar / International |
| System | Aware Vehicle Intelligence / Telematics |
| Component | Vref sensor supply — above normal range |
| Source address | Unknown or not applicable |
| Severity | medium |
| Review status | ai source checked |
| Source confidence | high |
| Last reviewed | 2026-03-26 |
Plain-English Meaning
Vref is the reference voltage the Aware module provides to its analog input sensors — typically 5 volts. This supply powers sensors connected to the analog inputs and sets the voltage reference for the 5-point calibration curves. When Vref is outside its expected range, all analog input readings that depend on it will be unreliable, and other analog input faults may appear as secondary effects.
Navistar S08312 maps Navistar Aware SPN 1079 FMI 0 to Vref Sensor Supply voltage — Data valid but above normal operational range at Black connector Pin 4. The fault activates when Vref deviates from the 4.8–5.1 V normal range (for FMI 0/1) or crosses absolute limits above 7 V or below 0.5 V (for FMI 3/4).
Common Symptoms
- Multiple analog input faults may appear simultaneously if Vref is the supply for multiple sensors
- Analog input readings may be incorrect across all inputs using Pin 4 as their reference
- Aware module may report inaccurate sensor data for all Vref-referenced inputs
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- External sensor or load connected to Pin 4 that draws excessive current and pulls Vref down
- Short to ground on the Vref circuit pulling the voltage below specification
- Short to supply driving Vref above 5 V
- Internal Aware module Vref regulator fault
First Checks
- Measure the voltage at Black connector Pin 4 with all sensors connected.
- Disconnect the sensors from the Vref-supplied inputs one at a time — if the voltage returns to normal after disconnecting a specific sensor, that sensor or its wiring is loading or shorting the Vref supply.
- Check for wiring faults that connect Pin 4 to a power or ground circuit.
- If Vref is abnormal with all analog inputs disconnected, the Aware module's internal regulator may be the source.
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
Will a Vref fault cause false readings on all analog inputs?
Yes. Any analog input configured to use Vref as its reference will report values relative to the actual (abnormal) Vref rather than the nominal 5 V. A Vref that is low will make all sensor readings appear compressed; a Vref that is high will make them appear expanded. Fixing the Vref fault first is essential before evaluating individual analog input readings.
How much current can the Aware module's Vref supply provide?
The Vref output has a defined current limit specified in the Navistar S08312 documentation. Connecting sensors that exceed this limit will cause Vref to droop. If multiple sensors are powered from Pin 4, verify that their combined current draw is within the Aware module's Vref supply specification.
Is Navistar Aware SPN 1079 FMI 0 a vehicle safety issue?
Vref faults affect the accuracy of body-builder and telematics inputs — they do not directly affect engine, brake, or powertrain systems. However, if a safety-related accessory (such as a temperature sensor for a refrigerated body or a pressure sensor for a PTO system) is powered by Vref, its readings may be unreliable while the fault is active.