It listens for every firing event and retards the timing 3deg every time it hears a knock. If it doesn't hear a knock it puts back one degree each event. so it would take three firing to get back.

This is done independently for each cylinder and they can generally go retarded 15 degrees from the mapped position.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician