AL18
FG Wilson
Engine ECU to Controller Communication Loss
Controller shows AL18 – CANbus Communication Error (on electronic engines)
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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 CANbus wiring between ECU and controller, Incorrect termination resistors, Faulty engine ECU, Electrical noise or grounding issues
How to Fix / Troubleshooting
Safety first: Stop the generator and isolate battery negative. Do not unplug ECU connectors with power applied.
- Inspect CANbus harness: Trace the twisted pair CAN wires from the engine ECU to the controller. Look for cuts, abrasions, or crushed sections.
- Check connectors: Unplug and re-seat the ECU and controller CAN connectors, inspecting for bent pins or corrosion.
- Verify termination: Ensure that 120 Ω termination resistors are present at each end of the CANbus as specified by FG Wilson.
- Measure bus resistance: With power off, measure resistance between CAN-H and CAN-L; it should be around 60 Ω for two 120 Ω terminators in parallel.
- Test run: Reconnect battery, clear the alarm, and attempt a start. If communication errors persist, the ECU or controller may require professional diagnosis.
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Repair Difficulty
Professional Required
5/5
Required Part
Engine ECU CANbus Harness
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