Cummins ISB CM850 (2003-06) Fault Code: 237 PID: SID 30 SPN: 644 FMI: 2 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.

The J1939 datalink connections are part of the OEM harness. Location of the J1939 harness will vary by the OEM. Refer to the OEM manual for specific component location.

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.

Possible repairs:

1)Repair or replace the OEM harness.