CM850 Electronic Control System – FAULT CODE 441

Battery 1 Voltage – Data Valid but Below Normal Operational Range – Moderately Severe Level


Fault Code: 441
PID: S168
SPN: 168
FMI: 1/18
LAMP: Amber

Battery 1 Voltage – Data Valid but Below Normal Operational Range
– Moderately Severe Level. ECM supply voltage is below the minimum system voltage level.

Engine may stop running or be difficult to start.

Unswitched Battery Supply

Circuit Description

The ECM receives constant voltage from the batteries through the unswitched battery wires that are connected directly to the positive (+) battery post. There is one 30-amp fuse in the unswitched battery wires to protect the OEM harness. In marine applications this is a 25 ampere fuse on 12V systems and a 15 ampere fuse on 24V systems. The ECM receives switched battery input
through the vehicle keyswitch wire when the vehicle keyswitch is turned on. The battery return wires are connected directly to the negative (-)
battery post.

Component Location

The ECM is located on the intake side of the engine. The ECM is connected to the battery by the OEM harness. This direct link provides a constant power supply for the ECM. In marine applications only circuits 1 and 3 are used for unswitched battery. The location of the battery will vary with the OEM. Refer to the OEM manual for battery location.

Shop Talk

This fault code is logged when the ECM battery supply voltage drops below 6 volts.

  • Verify that the ECM unswitched power is coming from the batteries and not the starter or other device. Check for possible weak batteries.
  • If the ECM unswitched battery supply is taken from the starter, check for low voltage during cranking. Low voltage during cranking can cause the ECM power supply to drop below specifications and log Fault Code 441.

Refer to Troubleshooting Fault Code t05-441

Last Modified:  08-Jul-2010