there's been a few posts recently about testing sensors, coils, etc. The FSM defines several tests using a basic volt/ohm/ammeter (VOM). These tests usually involve measuring resistance between two terminals. These tests are NOT conclusive -- in some cases they may indentify a faulty component, but just because a part "passes" the VOM test doesn't mean it is OK.

A good example is the knock sensor. The FSM states the KS is "OK" if its DC resistance is between 500k-620k ohm (or something like that - I don't have the FSM handy at the moment). Now, if you meausure it and find either an open or a short, then you can be assured your KS is faulty -- but just because you get, say, 540k doesn't mean it's necessarily "OK".

in fact, my KS did test "OK" but I still had the KS code. after a few days of troubleshooting (cleaning grounds, checking connections, etc) and clearing the codes several times to no avail, I finally replaced the damn thing and the code looks to be gone for good now.

the coils are another part that can give a "false negative" with a VOM test.