SPN 630 - FMI 2 (Fault Code 341)

Engine Control Module Data Lost - Data Erratic, Intermittent or Incorrect

Unswitched Battery Supply Circuit

Fault Code: 341
PID(P), SID(S): S253
SPN: 630
FMI: 2/2
Lamp: Amber

REASON: Engine Control Module Data Lost - Data Erratic, Intermittent or Incorrect. Severe loss of data from the ECM.

EFFECT: Possible no noticeable performance effects, engine dying or hard starting. Fault information, trip information, and maintenance monitor data can be inaccurate.

Circuit Description:
The Electronic Control Module (ECM) receives constant voltage from the batteries through the unswitched battery wires that are connected directly to the positive (+) battery post. There is a single 30-ampere fuse in the unswitched battery wires to protect the engine harness from overheating. In marine applications this is a 25 ampere fuse on 12 VDC systems and a 15 ampere fuse on 24 VDC 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. Pins 2 and 3 are optional circuits possibly not used by the OEM. In marine applications only circuits 1 and 3 are use for unswitched battery. Refer to the OEM circuit diagram or wiring diagram for detailed information on these circuit.

Component Location:
The ECM is located on the left side of the engine, near the front of the engine. The ECM is connected to the battery by the ECM power harness. This direct link provides a constant power supply for the ECM. The location of the battery will vary with the OEM.

Read More:
SPN 654 - FMI 5 (Fault Code 332)
SPN 110 - FMI 2 (Fault Code 334)


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