SPN 644 - FMI 2 (Fault Code 237)

External Speed Command Input (Multiple Unit Synchronication) - Data Erratic, Intermittent, or

Multi-Unit synchronization

Fault Code: 237
PID(P), SID(S): S030
SPN: 644
FMI: 2
Lamp: Amber

REASON: External Speed Command Input (Multiple Unit Synchronization) - Data Erratic, Intermittent, or Incorrect. The throttle input signal to the primary or secondary engine for multiple unit synchronization is less than 3 percent or more than 97 percent.

EFFECT: Primary or secondary engines may be shutdown.

Circuit Description:
The primary engine broadcasts the engine speed control message over the J1939 datalink to all secondary engines. Jumper wires are used to configure an engine as a primary engine or as a secondary engine. Only one engine can be configured as the primary engine. Up to five engines can be configured as secondary engines on the same J1939 datalink.

Component Location:
The J1939 datalink connections are part of the OEM harness. Location of the J1939 harness will vary by the OEM.

The configuration of the three pins inputs to the electronic control module (ECM) on the OEM harness determines if an engine is a primary or secondary engine. To activate a pin, the pin must be grounded. To deactivate a pin, the pin must be open circuit.

Read More:
SPN 108 - FMI 4 (Fault Code 222)
SPN 111 - FMI 1 (Fault Code 235)


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