The mower reports the collision sensor itself as defective rather than merely activated. Work through the physical causes first anyway — they are free to check and they produce the same symptom — but if it survives that, this one ends at a dealer.
Common causes
A genuine failure of the sensor or its wiring.
Impact damage, often from a collision weeks earlier that seemed harmless at the time.
Debris or a badly seated body holding the sensor permanently triggered.
A temporary electronic or firmware problem.
How to fix it
Brush out the body-to-chassis gap and confirm the body seats properly and moves freely — a jammed body can present as a defective sensor.
Look for cracks or a body sitting out of true after any hard collision.
Restart the mower, using “Reset Error” in the app first if it is offered.
If the fault returns straight after a restart, stop clearing it and book it in with a dealer. A safety sensor that keeps reporting itself defective is not one to keep resetting.
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MowerWatch is an independent product, not affiliated with, endorsed by, or sponsored by Husqvarna AB. Automower® is a registered trademark of Husqvarna AB, used only to describe compatibility. Codes and guidance are provided in good faith — always follow your model's operator manual and consult a dealer for repairs. · All error codes · Guides