The fealess trait says "the character is immune to fear and pinning" p118

When a kill team is subject to a fear effect they loose cohesion"unless the kill team leader passes a willpower test" p277

If the kill team leader is fearless do they still have to make the willpower test for the kill team?

OK I should have searched the forum first. I see t has come up a few times before with no clear answer but lots of the answers lean in the direction of the fearless squad leader passing the test automatically.

Probably. If nothing else they're leading by example, even if they're Fearless. If the Willpower roll fails, it's not so much that the Fearless guy (or anyone) feels fear, it's that the rest of the squad (and possibly even the leader) feels a trepidation in their ability to win that gives them pause and shatters their unity.