AL18
Kohler-SDMO CANbus Communication Fault

Controller displays AL18 / CAN Communication Error between engine ECU and APM controller

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Broken or loose CANbus wiring between ECU and controller, Incorrect CAN termination resistor, Faulty engine ECU, Electrical noise or grounding issues

How to Fix / Troubleshooting

Safety first: Turn controller to OFF and disconnect battery negative before accessing control wiring. Avoid ESD damage to electronic modules.

  • Inspect CAN wiring: Locate the twisted pair CAN-H and CAN-L wires between the engine ECU and APM controller. Check for cuts, abrasions, or loose connectors.
  • Check termination: Verify that termination resistors are installed as specified (typically 120 Ω at each end of the bus). Measure resistance between CAN-H and CAN-L with power off; it should be around 60 Ω for two terminators.
  • Secure connectors: Reseat ECU and controller connectors. Look for bent pins or corrosion.
  • Grounding: Ensure the controller and ECU share a solid common ground and that there are no ground loops.
  • Reset and test: Reconnect battery, clear AL18, and start the generator while monitoring for communication status.

If CAN errors persist, the ECU or controller may be defective and require replacement by an authorized service center.

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Repair Difficulty

Professional Required 5/5

Required Part

Engine ECU / CANbus Harness
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