PACCAR PX-9 CM2350 (2013-17) Fault Code:237 PID:SID 30 SPN:644 FMI:2 External Speed Command Input (Multiple Unit Synchronization) – Data Erratic, Intermittent, or Incorrect

Reason:
Multiple Unit Synchronization Switch – Data Erratic, Intermittent, or Incorrect. Multiple unit synchronous ON/OFF switch and multiple unit synchronous

Effect:
The multiple unit synchronization feature will be disabled

Circuit Description:
The multiple unit synchronization feature uses an ON/OFF switch and a complementary switch. The complementary switch is used by the ECM to determine the type of coupling (hard or soft) to use between multiple engines when the multiple unit synchronization switch is engaged/installed by the OEM to support this feature.

Component Location:
The multiple unit synchronization switch is mounted by the OEM. Refer to the OEM manual for specific switch location.

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected the multiple unit synchronous ON/OFF switch and multiple unit synchronous complimentary ON/OFF switch have different values.

Action Taken When the Fault Code is Active:
1) The ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.
2) The multiple unit synchronization feature is disabled.

Conditions for Clearing the Fault Code:
1) To validate the repair, start the engine and let it idle for 1 minute.
2) The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
3) The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
4) The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults.

Shop Talk:
The multiple unit synchronization feature allows two or more engines to be controlled by a single throttle signal and run at a similar speed. There are three engine configurations available with this feature: soft coupled, hard-coupled, and soft-coupled marine. The soft-coupled configuration has all secondary engines in parallel with each other. The primary engine outputs a throttle signal to all secondary engines. This setup allows all engines to remain running, if a secondary engine stops.

Possible Causes:
1) Damaged pins
2) Open circuit
3) Short circuit to engine block ground
4) Faulty engine harness connector

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