Snark mode = ON
I can just hear the people over at ******** telling you, "Just go over to BassesByLeo and grab the K mod diagram. It's all you'll need."
WRONG!Snark mode = OFF (mostly)
Rant mode = ON
The K model basses originated in basses built for Kurosawa (hence the "K") and the Japanese market. They were available here as a no cost off-menu option, and I believe they are now listed on the Options sheet.
The L-2000/2500/ASAT K model basses are distinct from the non-K models. The pickups are different, the coil select switch is different, and the coil select switch is wired differently than the "Daveplaysbass" mod (which is what you should be doing).
People call what you're doing the K mod because they think it's just a modification to the standard circuit, and as you've found that name leads to a lot of confusion. People generally don't know that the circuits are actually different, nor do they dig in looking for the GOTCHA that's currently biting you. Good questions might be: "What is a K model bass?" "Other than the obvious, what makes a K model bass different from its non-K brethren?" And so on.
Rant mode = OFF
What you're doing is NOT a K mod, but a single coil mod. Look carefully at the diagram you posted above. See the 5-lead pickups? That isn't what you have. Daveplaysbass designed his circuits around the 4 lead pickups that most of us have. You're trying to use your 4-lead pickups in a circuit they're not designed for.
This is a circuit for my L-2500. It is WAY different than a stock circuit, but the coil select and pickup select switches are what you need.
Click the image for a PDF.
You'll need the coil select switch specified in the circuit comments (you may already have this). Disregard everything in the diagram except for the coil select switch, the pickup select switch, and their various inter-connections. The connections at the pickup select switch can be used as a reference to make sure you do it right.
Best of luck.
Ken...