S65 Throttle Actuators: The Failure Everyone Defers

The S65 is a robust engine with two well-known service items: rod bearings and throttle actuators. The second gets far less attention, and it is the one that leaves people stranded.

The symptom

A limp-mode warning, reduced power and a stored fault for throttle adaptation. Often it is intermittent at first, appearing only on cold mornings, which is exactly why it gets ignored.

The cause

Each bank has an actuator driving eight individual throttle bodies. The internal gears and the potentiometer wear, and the actuator loses its ability to report position accurately.

The fix

Rebuild services exist and are the sensible option, costing a fraction of new units. Do both banks at once. Budget a day of labour and expect the car to feel noticeably crisper afterward, because most owners have been driving with degraded response for months.