لغزش پک کلاچ چهارچرخ‌محرک

The clutch pack distributing torque to the secondary axle, slipping. It is designed to slip briefly — that is how it modulates torque — so the fault is slip that continues when it should have locked.

The module detects it by comparing axle speeds: a difference that persists while the clutch is commanded closed is slip, and it stores a performance fault. The complaint is a vehicle that has quietly become two wheel drive, noticed only when traction is needed. Fluid is the first thing to check: these packs use a specific fluid whose friction characteristics are the whole mechanism, and a service interval missed or the wrong fluid used produces exactly this. Worn plates are the other answer and are an internal repair, so confirm the fluid before committing.