For years I just used the standard 2.5 mm pins that are used all over the car to make individual test leads with a small piece of heat shrink over them.
I then got around to making up a proper test lead with a plug from an older Diesel tach amplifier which plugs into that socket. There are many defective ones around out there. I removed and tossed the circuit board, connected my wires and added a strain relief. Works great.