Navistar Aware SPN 168 FMI 3 — Power supply — voltage above normal

Code Details

Plain-English Meaning

The Aware module is receiving more than 18 volts on its main power supply. On a 12-volt truck system, normal charging voltage is approximately 13.5–14.5 V. A reading above 18 V indicates an overcharging condition, a wiring fault that connects the Aware module to a higher-voltage circuit, or a faulty alternator voltage regulator.

Navistar S08312 maps Navistar Aware SPN 168 FMI 3 to Battery Potential — voltage above normal or shorted high at Black connector Pin 1. The fault activates when the measured voltage exceeds 18 volts for more than 1 minute.

Common Symptoms

• Aware Vehicle Intelligence alert active
• Other 12 V electrical components may also be damaged or showing faults if the overvoltage is system-wide
• Fault may correlate with high engine RPM, alternator replacement, jump-starting, or shore-power/charger connection
• Telematics module may reset or log communication gaps if the overvoltage protection circuit intervenes

Possible Causes

Possible causes may include the items below. The list is not a parts diagnosis.

• Alternator voltage regulator failed, allowing charging voltage to rise above specification
• Wiring fault connecting the Aware module's supply to a 24 V circuit on a dual-voltage system
• Converter or upfitter-installed equipment generating overvoltage on the circuit powering the Aware module
• Incorrect battery charger or booster connected during service work
• Poor battery ground allowing voltage spikes at the module when load changes quickly

First Checks

• Measure the voltage at Black connector Pin 1 with the engine running — confirm whether the overvoltage is present at the module.
• Measure the charging system voltage at the battery with the engine running — if it also reads above 15 V, the alternator or regulator is the source.
• If the charging voltage is normal but the Aware module supply is high, look for a wiring fault on the Aware supply circuit.
• Check whether an upfitter power converter, auxiliary battery charger, or inverter is tied into the same feed as the Aware module.
• Do not continue operating with confirmed sustained overvoltage — it can damage the Aware module and potentially other electronics.

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

• SPN 168 topic page
• FMI 3 explanation
• Navistar / International manufacturer hub
• Telematics fault codes
• Search this code