Volvo All Engines (2004 Emissions) Fault Code: PID 158 FMI 4 Battery Voltage

Fault Condition: Code PID 158 will set with an FMI 3 if the voltage rises above 19 volts (12 volt system) or above 36 volts (24 volt system). FMI 4 will set when the battery voltage falls below 9 volts (12 volt system) or below 17 volts (24 volt system). Damage to the modules and its components may occur with high battery voltages.

Possible repairs:

1) Verify that code PID 158 is set. If code PID 158 is not set, wiggle the harness and connectors to try to set the code.
2) Check the Failure Mode Identifier (FMI) using a diagnostic computer. If the FMI is 3 (voltage too high), check the vehicles charging system. The generator may be overcharging the batteries. Perform vehicle charging system testing and diagnosis. If the FMI is 4 (voltage too low), check the vehicle’s charging system and external charger if equipped. Perform vehicle charging system testing and diagnosis.