Beneath that heatshrink is effectively a Raychem solder junction. The wicking process is halted when a solder block is placed on the strands. The early M271 engine, which had issues with the camshaft adjuster magnets, was the reason Mercedes made these. Interestingly, the issue didn't arise until Mercedes abandoned the long-used configuration of their wiring plugs. Modern techniques involve crimping tiny pins to the copper strands instead of soldering them, as opposed to the previous method of using large, spherical pins. Unchecked, the oil will wick up the copper to the other end, which is shocking to some.