John Deere 200149 – Left Control Unit: Serial Communication Link Problem Between Left Control Unit and Control Relay Board

The fault code indicates a problem in the serial communication link between the Left Control Unit (LCU) and the Control Relay Board. This issue disrupts the proper exchange of data between these two essential components. It is classified as a Priority 2 or 3 fault, meaning it should be checked immediately but may not require an immediate shutdown of the machine.

• 9450
• 9550
• 9650
• 9540 WTS
• 9560 WTS
• 9580 WTS
• 9640 WTS
• 9660 WTS
• 9680 WTS
• 9560 STS
• 9660 STS
• 9760 STS
• 9860 STS
• 9650 STS
• 9750 STS
• 9660 CTS

1. 1

   Visually inspect the wiring harness and connectors between the Left Control Unit and the Control Relay Board for any visible signs of damage, such as chafing, corrosion, or loose connections

2. 2

   Check power and ground connections to the Control Relay Board, including inspecting the F20 fuse in the engine compartment relay panel

3. 3

   Perform a controller reset by turning the key switch to the 'OFF' position, waiting for 30 seconds, and then restarting the machine, or by disconnecting and reconnecting the control unit connectors

1. 1

   Isolate the Issue

   Based on the diagnostic checks, determine if the fault lies with the wiring, the Control Relay Board, or the Left Control Unit.

2. 2

   Repair Wiring

   If damaged wiring or connectors are found, repair or replace the affected sections of the harness.

3. 3

   Replace Components

   If the wiring is intact, the issue may be with either the Control Relay Board or the Left Control Unit. Replace the suspected faulty component. Note that some control units may require programming by a John Deere dealer after installation.