اتصال ضعیف تغذیه دائم

High resistance in a module's permanent live feed. The distinction from a blown fuse is that everything appears to work — the module powers up, communicates and answers questions, and only loses its memory when the vehicle sleeps and the current available through a resistive joint is not enough to hold it.

So the symptoms are intermittent and look like software: adaptations occasionally lost, a clock that sometimes resets, keep-alive memory codes appearing at random. Measure voltage drop on the permanent feed with the vehicle asleep rather than resistance at rest, which a marginal joint passes easily. Corroded joints behind trim or at a body earth are the usual place, and a supplementary lead fitted temporarily is a quick confirmation.